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A joint initiative of Australian, State and Territory and New Zealand

Governments.

Product Profile: Solar Water

Heaters

August 2014

Product Profile: Solar Water Heaters ii

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© Commonwealth of Australia (Department of Industry) 2014.

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ISBN: 978-1-925092-39-4 [ONLINE]

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Product Profile: Solar Water Heaters iii

CONTENTS ...................................................................................................................................................... III Glossary and abbreviations ............................................................................................................................. vi System identification key ................................................................................................................................ vii

EXECUTIVE SUMMARY ................................................................................................................................... 1

OVERVIEW, FINDINGS AND QUESTIONS ..................................................................................................... 1 Introduction ....................................................................................................................................................... 1 Solar Water Heaters .......................................................................................................................................... 2 Solar water heater market ................................................................................................................................ 2 Solar water heater testing ................................................................................................................................. 3 Compliance, auditing and checking ................................................................................................................. 6 Conclusions........................................................................................................................................................ 6 Possible policy options ...................................................................................................................................... 6 Where to from here? ......................................................................................................................................... 6 Guiding questions for stakeholder submission ............................................................................................... 7

1. SOLAR WATER HEATERS .................................................................................................................. 9 Types of systems ................................................................................................................................................ 9 System components ......................................................................................................................................... 11 System operation .............................................................................................................................................. 12

2. ENERGY USE AND GREENHOUSE GAS EMISSIONS CHARACTERISTICS ................................ 13 Energy consumption characteristics ............................................................................................................... 13 Energy costs ...................................................................................................................................................... 15

3. GOVERNMENT/POLICY CONTEXT .................................................................................................. 19 Regulations and regulators .............................................................................................................................. 19 Equipment Energy Efficiency Program ......................................................................................................... 20 Standards ......................................................................................................................................................... 20 Building codes ................................................................................................................................................. 20 Rebates & incentives ....................................................................................................................................... 22

4. MARKET CHARACTERISTICS .......................................................................................................... 23 Cost .................................................................................................................................................................. 23 Sales and stock ................................................................................................................................................ 24 Manufacturers and suppliers .......................................................................................................................... 28 Market trends .................................................................................................................................................. 29

5. PRODUCT PERFORMANCE .............................................................................................................. 30 Performance claims ......................................................................................................................................... 30

6. SOLAR WATER HEATER TESTING ................................................................................................. 32 Tank test results .............................................................................................................................................. 32 Collector test results ........................................................................................................................................ 38 Full physical system tests and model checking ............................................................................................. 40 TRNSYS modelling of test results .................................................................................................................. 49

7. MARKET FAILURES, BARRIERS AND ENERGY EFFICIENCY ...................................................... 57 Market failures ................................................................................................................................................ 57 Other market barriers ..................................................................................................................................... 59

Contents

Product Profile: Solar Water Heaters iv

8. SUMMARY AND DISCUSSION .......................................................................................................... 62

9. RESOURCES ...................................................................................................................................... 63

APPENDIX 1: STANDARDS .......................................................................................................................... 65

APPENDIX 2: STATE AND TERRITORY REBATES .................................................................................... 68

APPENDIX 3: MANUFACTURERS’ CLAIMS ................................................................................................ 72 Manufacturers’ claims on tested electric boosted solar water heaters ......................................................... 73 Manufacturers’ claims on tested gas boosted solar water heaters ............................................................... 75

APPENDIX 4: TEST RESULTS ...................................................................................................................... 78 Additional results on tank heat loss ............................................................................................................... 78 Additional information on heat loss and air temperatures .......................................................................... 79 Additional data on system heat loss and energy savings .............................................................................. 80 Field test results for Model E1 ........................................................................................................................ 80 Additional data on the Scenario 2 field tests ................................................................................................. 82 Additional data on the field tests .................................................................................................................... 83 Additional data on pipe insulation and pipe length ...................................................................................... 83 Collector test results ........................................................................................................................................ 86 Additional data on collector freeze testing .................................................................................................... 86 Additional data on freeze tests and energy savings modelling ..................................................................... 92

APPENDIX 5: SOLAR WATER HEATER BRANDS ...................................................................................... 95

APPENDIX 6: DISCUSSION OF OPTIONS ................................................................................................... 97

LIST OF TABLES

Table 1: Average capital cost in Australia (including installation) by water heater type, 2008-2012 ............... 23 Table 2: Australian water heater stock and sales ................................................................................................. 24 Table 3: Water heater stock in 2012, by state (%) ................................................................................................ 24 Table 4: Estimated 2012 New Zealand water heater stock .................................................................................. 27 Table 5: 2012 water heater sales in New Zealand ................................................................................................. 28 Table 6: Australian SWH market penetration by percent of sales and brand, 2008-12 .................................... 28 Table 7: Water heater stock, by year (%)............................................................................................................... 29 Table 8: Measured volume and hot water delivery for electric boosted systems ............................................... 34 Table 9: Measured volume and hot water delivery for gas boosted systems ...................................................... 34 Table 10: Summary of freeze test results .............................................................................................................. 40 Table 11: Comparison of energy from model and physical test during Scenario 2 ............................................. 45 Table 12: Comparison of nominal and determined gas consumption ................................................................. 47 Table 13: Thermal efficiency of all gas boosted systems ...................................................................................... 48 Table 14: Difference between modelled and measured heat loss during freeze testing ..................................... 52 Table 15: Summary of Australian state and territory SWH rebates .................................................................... 70 Table 16: Manufacturers claims on tested electric boosted solar water heaters ................................................. 73 Table 17: Manufacturers’ claims on tested gas boosted solar water heaters ....................................................... 75 Table 18: List of SWH brands sold in Australia and New Zealand ...................................................................... 96

LIST OF FIGURES

Figure 1: Close-coupled thermosiphon ................................................................................................................. 10 Figure 2: Split system ............................................................................................................................................. 10 Figure 3: Flat plate thermosiphon (left) and evacuated tube split system (right) ............................................... 11 Figure 4: Energy profile of a solar water heater .................................................................................................... 14 Figure 5: Electricity consumption in New Zealand ............................................................................................... 15 Figure 6: Residential electricity price movements in Australia - 2011/12 to 2014/15 ........................................ 16 Figure 7: New Zealand residential electricity price forecast to 2040 ................................................................... 16 Figure 8: Average household gas bills by state ...................................................................................................... 17

Product Profile: Solar Water Heaters v

Figure 9: New Zealand residential gas price forecast to 2040 .............................................................................. 17 Figure 10: SWH installations by year and climate zone ....................................................................................... 25 Figure 11: SWH installations by year and state/territory .................................................................................... 26 Figure 12: Solar water heaters installed by market segment ............................................................................... 26 Figure 13: Solar and heat pump water heater installations in New Zealand between 2001 and 2012 .............. 27 Figure 14: SWH tank heat loss compared to MEPS level for ESWHs ................................................................. 33 Figure 15: System heat loss compared to tank heat loss at 20oC ......................................................................... 35 Figure 16: Annual average daily mean temperature in Australia 1961-1990 ...................................................... 35 Figure 17: Median annual average temperature in New Zealand ........................................................................ 35 Figure 18: System heat loss at various air temperatures...................................................................................... 36 Figure 19: Instantaneous collector efficiency ....................................................................................................... 39 Figure 20: Cumulative energy use for Scenario 1 .................................................................................................. 41 Figure 21: Energy use for Model E1 (SE250) during the Scenario 1.................................................................... 42 Figure 22: Comparison of energy used for Model E1 (SE250) during Scenario 1 .............................................. 43 Figure 23: Cumulative energy use for Scenario 2 ................................................................................................. 44 Figure 24: Comparison of energy used by reference electric system during Scenario 2 .................................... 45 Figure 25: Cumulative water delivered for Scenario 3 ......................................................................................... 46 Figure 26: Average weekly irradiance and amount of hot water delivered, as a percentage of tank volume,

during Scenario 3 ................................................................................................................................................... 47 Figure 27: Impact of boosting method on energy savings for Model E2............................................................. 50 Figure 28: Impact of boosting method on energy savings for Model E1 .............................................................. 51 Figure 29: Modelled annual energy savings for electric boosted SWHs ............................................................. 53 Figure 30: Comparison of current and modelled STC entitlements for electric boosted systems .................... 54 Figure 31: Comparison of modelled STC entitlements using tank and system heat loss ................................... 54 Figure 32: Modelled annual energy savings for gas boosted SWHs .................................................................... 55 Figure 33: Comparison of current and modelled STC entitlements for gas boosted systems ........................... 56 Figure 34: SWH climate zones for Australia and New Zealand ........................................................................... 78 Figure 35: SWH tank heat loss compared to MEPS level for ESWHs (adjusted to closest MEPS step) ........... 79 Figure 36: Difference between using tank and system heat loss to model energy savings for electric boosted

SWHs....................................................................................................................................................................... 80 Figure 37: Energy use and system temperatures for Model E1 over a 24-hour period ...................................... 81 Figure 38: Cumulative water delivered for Scenario 2 ......................................................................................... 82 Figure 39: Average daily hot water delivery and element energy use for Scenario 2 testing ............................. 82 Figure 40: Cumulative irradiance for all three scenarios .................................................................................... 83 Figure 41: Sensitivity to variation of pipe insulation thickness for electric boosted split systems .................... 84 Figure 42: Sensitivity to variation in pipe length for electric boosted split systems .......................................... 85 Figure 43: Sensitivity to variation of pipe insulation thickness for electric boosted thermosiphons ............... 85 Figure 44: Modelled difference in energy savings between indoor and outdoor collector tests ....................... 86 Figure 45: Model E3 (SF270) freeze test results .................................................................................................. 87 Figure 46: Model E4 (SF325) freeze test results .................................................................................................. 87 Figure 47: Model E6 (TF305) freeze test results .................................................................................................. 88 Figure 48: Model E7 (TF330) freeze test results .................................................................................................. 89 Figure 49: Model E8 (TF300) freeze test results ................................................................................................. 90 Figure 50: Model E2 (SF415) freeze test results .................................................................................................... 91 Figure 51: Model E1 (SE250) freeze test results .................................................................................................... 91 Figure 52: Model E5 (SE340) freeze test results .................................................................................................. 92 Figure 53: Actual (top) and modelled (bottom) freeze test results for Model E4 (SF325) ................................ 93 Figure 54: Actual (top) and modelled (bottom) freeze test results for Model E5 (SE340) ................................ 94 Figure 55: Proposed EU solar water heater label ............................................................................................... 103

Product Profile: Solar Water Heaters vi

Glossary and abbreviations

ACOSS Australian Council of Social Service

AEMC Australian Energy Market Commission

AGA Australian Gas Association

BASIX Building Sustainability Index

BCA Building Code of Australia

CER Clean Energy Regulator

CFL Compact Fluorescent Lamp

CLASP Collaborative Labelling and Appliance

Standards Program

COAG Council of Australian Governments

DMITRE Department of Manufacturing,

Innovation, Trade, Resources and

Energy (SA)

E2WG Energy Efficiency Working Group

E3 Equipment Energy Efficiency Program

EECA Energy Efficiency and Conservation

Authority (New Zealand)

EES Energy Efficient Strategies

ESC Essential Services Commission

(Victoria)

ESTIF European Solar Thermal Industry

Federation

ESWH Electric Storage Water Heater

GEM Green Energy Markets

GEMS Greenhouse and Energy Minimum

Standards Act 2012

GWA George Wilkenfeld and Associates

IEC International Electrotechnical

Commission

IPART Independent Pricing and Regulatory

Tribunal (NSW)

LPG Liquid Petroleum Gas

MCE Ministerial Council on Energy

MEPS Minimum Energy Performance

Standards

MWh Mega Watt hours

NCC National Construction Code

NEM National Electricity Market

NFEE National Framework on Energy

Efficiency

NHWSF National Hot Water Strategic

Framework

NSEE National Strategy on Energy Efficiency

NZBC New Zealand Building Code

NZEECS New Zealand Energy Efficiency and

Conservation Strategy

PCE Parliamentary Commissioner for the

Environment (New Zealand)

PV photovoltaic

REBS Renewable Energy Bonus Scheme

REC Renewable Energy Certificate

RET Renewable Energy Target

RIS Regulation Impact Statement

SANERI South African National Energy

Research Institute

SCER Select Council on Energy and

Resources

SRES Small-scale Renewable Energy Scheme

STC Small-scale Technology Certificate

SWH Solar Water Heater

TRNSYS Transient System Simulation Tool

VEEC Victorian Energy Efficiency Certificate

VEET Victorian Energy Efficiency Target

Product Profile: Solar Water Heaters vii

System identification key

When referring to test results within this document, a key has been used to describe each solar system rather

than using a brand name, system name and manufacturer’s model codes which vary in format. The key

indicates whether a system has electric or gas boosting, if it is a ‘split system’ or a ‘thermosiphon’ design, the

size of the tank and the type of collectors used. All gas boosted systems used flat-plate collectors but the key for

gas systems provides additional information on if an instantaneous or in-tank gas booster was used.

Electric boosted systems

Electric boosted Design identifier: S= Split system, T= thermosiphon

EX (S/T E/F 200) Tank size (litres)

Model identifier Collector identifier: E = Evacuated tube, F = flat plate

Gas boosted systems

Gas boosted Design identifier: S= Split system, T= thermosiphon

GX (S/T I/S 200) Tank size (litres)

Model identifier Booster identifier: I = Instantaneous, S = storage

E.g. Model E4 (SF325) is the fourth electric boosted systems tested and is a split systems design using flat

panel collectors and a 325L storage tank

Product Profile: Solar Water Heaters 1

Water heating in Australia and New Zealand is a major contributor to energy use and cost in the residential

sector, comprising approximately 25% of household energy use in Australia, and 30% in New Zealand. Water

heating is also a significant cost in many businesses and commercial organisations. The Commonwealth,

state and territory governments support improving the energy efficiency of appliances and equipment where

this will deliver benefits to households and businesses. Consequently, the Australian, state, territory and

New Zealand governments have agreed, through the Equipment Energy Efficiency (E3) Committee, to

undertake research on hot water technologies, including solar water heating, to better understand the market

and consider if there are any issues or need for improvements in energy efficiency. This report, the Product

Profile: Solar Hot Water Heaters summarises initial research and is published for all interested parties to

provide comments to help inform any possible action that may be considered in relation to improving the

energy efficiency of hot water appliances.

Solar water heaters (SWHs) are an established technology which can assist in reducing water heating energy

use. In Australia and New Zealand, SWHs are not subject to any mandatory energy efficiency regulations.

The residential, commercial and government sectors have all made substantial investments in solar water

heating technology through purchasing systems, innovation, installer and consumer education and rebate

programs. Potential improvements in either the sales or efficiency levels of SWHs present an opportunity for

households and businesses to lower their energy usage, save money, increase economic productivity and

reduce greenhouse gas emissions.

SWH sales comprise approximately 26% of the Australian and 4% of the New Zealand water heating markets.

There are many design approaches for SWHs and the performance of these heaters is also highly reliant on

the location and quality of the installation. As SWHs can be more expensive than other water heaters, it is

important that a household or business is able to choose the right system for their needs, this will ensure that

the consumer is able to minimise their ongoing energy costs and save money.

Given the benefits of this technology and the large investments made by stakeholders, the E3 Committee

commissioned research to see how this technology actually performs. SWHs are the last of the main water

heating technologies identified for investigation. To inform the development and findings of this Product

Profile, the E3 Committee conducted a series of physical performance tests against Australian/New Zealand

(AS/NZ) Standards. It also carried out a monitoring program of SWHs and a review of existing literature.

The overall findings of the E3 Committee are that while SWHs are a key hot water technology capable of

saving energy and money, recent energy efficiency performance testing has revealed discrepancies with

reported energy efficiency claims. Such discrepancies are not unexpected in products that are not subject to

independent testing and performance checking. Test results show that a number of components failed

existing AS/NZ Standards and some claims being made to consumers were overstated when compared to the

E3 Committee’s independent tests. Results also showed that the industry recognised computer model

(TRNSYS) used to claim ‘energy savings’ appears to be reasonable with generally only mild overstatements of

performance. However, faulty or poorly designed systems may not be correctly modelled and the behaviour

of some systems in cold areas is also not accurately accounted for – hence energy savings claims may not

reflect actual performance. In addition, there appear to be some poor installation practices that result in low

or no energy savings. Consumers appear to have limited success in either identifying poor performance

and/or having poorly performing systems rectified and there is little ‘comparative’ information to empower

consumers to choose the most appropriate water heater for their needs.

In light of the importance of these water heaters to the residential and commercial sectors and the issues

identified in this document, the E3 Committee is seeking views and dialogue with consumers, industry and

other stakeholders on experiences with the performance of SWHs and the SWH market. For example, is

there a need for government, industry or consumer groups to drive energy efficiency improvements in the

hot water sector? If so, should this be done by improving information, ensuring that current component-

based Standards are met or are the benefits of a ‘system based’ energy efficiency approach sufficient for this

to be considered? Comment on these issues will help to inform governments about the desirability of any new

approaches and the associated costs, benefits and risks.

Executive summary


This chapter provides a simplified summary of the report. Readers seeking further detail are encouraged to

read and consider the report in its entirety.

Introduction

Water heating in Australia and New Zealand is a major contributor to energy use in the residential and

commercial sectors. Solar water heaters (SWHs) present an opportunity for households and businesses to

save energy, save money and reduce greenhouse gas emissions over the life of the system when compared to

most other water heating technologies. Additionally, heating water with less electricity or gas improves

energy productivity and thereby, economic productivity.

Manufacturers, consumers and the government recognise the energy saving potential of SWHs and have

demonstrated support for this industry and product. Manufacturers are investing in this technology through

extensive research and development programs which have resulted in new and innovative systems appearing

on the market. Consumers are investing in this technology by purchasing and installing these systems in new

homes and using them to replace existing water heaters. The Government has also supported the

manufacturing industry and consumers through a range of rebates, grants and information programs which

have supported strong sales and encouraged investment.

SWHs are presented to the market as low running cost, low emission water heaters that operate much more

efficiently than conventional water heaters. However, given that SWHs account for 26% of water heaters

installed annually in Australia and SWHs are not currently regulated for energy efficiency, energy efficiency

claims are not checked or recorded. It is important that we find out how these systems are actually

performing due to the considerable investment being made by manufacturers, consumers and governments.

The joint Government Equipment Energy Efficiency (E3) Program tested a number of SWHs to inform this

document and has identified a number of issues around energy efficiency claims, system performance and

the information being provided to both residential and commercial purchasers of water heaters. It is

important to note that a properly chosen and installed SWH can be a very sound investment and save

substantial amounts of energy. The testing focused on residential SWHs and identified a number of issues

with the ‘energy savings’ computer model (TRNSYS) used by industry to underpin claims including:

• Claimed ‘energy savings’ are slightly higher than independent test results using the defined industry

endorsed method.

• Claims made under the ‘energy savings’ model may not reflect actual annual energy savings as it makes

assumptions that:

o components work as claimed – non-compliant and poorly designed components mean

claims may not be accurate

o system heat loss is not accurately modelled – testing showed many more systems may lose

heat/energy than assumed.

• Non energy-efficiency findings included systems not meeting ‘hail impact’ or ‘freeze tests’ – such systems

may fail.

Additional research of academic literature, studies and consumer feedback, has highlighted similar issues

identified in the E3 tests. The research and tests identified a degree of non-compliant or poorly operating

SWH components and indicated that many SWHs may either have incorrectly operating components or be

poorly installed. If this is the case the degree of energy savings (and hot water) that a consumer would expect

from their SWH may not be achieved in ‘real life’ installations.

Consequently, if business and residential energy savings claims are higher than what is independently

assessed with the recognised computer model and the independent results are also overstated compared to

what is occurring in the field, then there appears to be a clear gap between the energy savings that consumers

and business are told to expect from a solar system to what they actually receive. This ‘gap’ appears to be far

Overview, findings and questions


larger for systems that will be installed in cold locations which are generally the locations that have the

highest water heating needs.

In addition to the test results, the paper identifies concerns about consistency and reliability of information

on SWH performance, suitability and energy efficiency. Information provided by manufacturers can be

difficult to find or understand and without adequate information purchasers of SWHs may not be able to

make informed decisions on water heater purchases and identify the most suitable SWH for their situation.

Solar Water Heaters

SWHs heat water through the absorption of solar energy to heat and store water for later use. They can be

complex systems made up of many components, including solar collectors, storage tank, circulation pump

and booster. When correctly chosen, installed and operated, SWHs are highly efficient, as they are able to

heat as much hot water as a conventional gas or electric hot water system but using less energy. SWHs are

used in homes, businesses and industry.

There are two main types of solar water heating systems:

• Thermosiphon – the storage tank is mounted directly adjacent to the collector

• Split system – the storage tank is located separate to the collector, generally on the ground.

There are several components in a SWH system and their performance is affected by solar irradiance,

ambient air temperature and/or other climatic conditions. A brief description of the major components and

their functions is listed below.

• Solar collector – a device designed to absorb the sun’s radiant energy and transfer the thermal energy

gained to the fluid. Some systems on the market now use solar photovoltaic (PV) panels to generate

electricity to power an electric element.

• Storage tank – an insulated the vessel, including fittings, in which the heated water is stored. It may have a

booster to provide heating to supplement the solar input. Storage tanks can be located on the roof, inside

the roof cavity or on the ground, either inside or outside the house.

• Circulation pump – required in split-systems, to circulate water between the storage tank and collector. A

circulation pump may operate during periods of solar gain to transfer energy from the collector to the

storage tank, but may also need to operate in frost conditions to help prevent damage from fluid freezing

in the collector and/or pipes.

The installation of a SWH is much more complex than the installation of a conventional water heater. A SWH

that has been incorrectly installed may cause problems for the consumer that are costly to fix or affect the

performance of the system.

Solar water heater market

In the Australian market, SWHs made up approximately 12% of the installed water heater stock in 2012,

which had increased from 7% in 2008. Of these, 77% of installed SWHs are electric boosted and 23% are gas

boosted. In New Zealand, SWHs have a low market share of 1.6%, because conventional electric water

heaters have been, and remain, the dominant player in water heating. Of the SHWs installed, electric split

systems are most common in the New Zealand, with the storage tank often located inside the house so that it

is not exposed to extreme winter weather conditions (wind and temperature).

The most important drivers influencing the sales of SWHs include:

• Rate at which water heaters in existing dwellings are replaced and the pace of new home construction;

• Purchase and installation costs compared to other water heater types;

• Expected savings in energy costs;

• Consumer perceptions of energy prices;

• Access to reticulated gas;

• Financial incentives and rebates; and

• Some jurisdictional regulatory requirements (such as those found in the Australian National Construction

Code (NCC)).


Solar water heater testing

The performance of a SWH depends on a greater number of factors than a conventional electric or gas

storage water heater. Performance, including electricity/gas consumed, amount of hot water supplied and

overall energy efficiency can all vary, depending on the following:

• Location and climate where it is installed and temperature of incoming water;

• Installation quality, thermostat and control strategy settings;

• Heat loss from the storage tank, pipes and collector;

• Water usage pattern (quantity, duration and time of day); and

• Heating efficiency of the system and whether the booster is on continuous, timer-based or manual

operation.

The systems tested were chosen to ensure that a wide range of system, tank and component types were

tested. These tests were designed to provide an understanding of the total efficiency and performance of a

system through both tests to existing standards and field trials.

Heat loss – storage tank only

The storage tank for a hot water system can be thought of as a large thermos flask. Hot water stored in the

container will gradually lose heat and cool over time. A ‘standing heat loss test’ applied to storage tanks of

conventional electric storage water heaters (ESWHs) measures the amount of energy required by the storage

tank to maintain a constant water temperature of 75°C in an air temperature of 20°C. SWH tanks are not

required to meet requirements against this test, but test results do provide insights into how well SWHs are

able to store hot water. The results indicated that 70% of SWH tanks tested would not have met the ESWH

minimum requirement. Ideally SWH tanks should be capable of storing useable hot water with minimal heat

loss for extended periods such as a series of cloudy days.

Heat loss – complete system

In ‘real life’ a SWH will lose heat from the insulated storage tank, solar collectors, pipes between the

collectors and tank and tank fittings - more sources of heat loss than a conventional water heater.

Whilst the ‘standing heat loss’ storage tank-only test is an important measure of the ability of a SWH to store

hot water, the test defined in the Standard is performed at 20°C with only very light breeze. This means the

test conditions are not representative of the temperature or wind conditions experienced by the majority of

the installed SWHs in Australia and New Zealand (for tanks installed outside). These are both factors that

drive heat loss.

To gain a better insight into how much heat a SWH (with all the components) would lose under different

conditions, a series of tests were carried out at temperatures ranging from 2°C to 35°C. Results predictably

indicated that the system heat loss at 2°C was significantly higher than the tank-only ‘standing’ heat loss at

20°C. Heat losses can be further magnified when some systems pump hot water from the tank into the

collectors in order to prevent frost damage. This occurred during our tests for one of the two split systems

with the heat loss being equivalent to about 50% of the energy that a two person household in Melbourne

uses per day in winter. This energy loss was with no hot water being supplied i.e. all the energy was ‘lost’ to

the surrounding air.

The high energy losses demonstrated by these tests in cold conditions have implications for the suitability of

some solar systems for climates where winter temperatures can be very low for significant portions of the day

and night for a number of months.

Resistance to freezing and associated heat losses

Resistance to freezing is very important in many areas of Australia and New Zealand as some systems may

break if fluids freeze and expand in low temperatures. All solar collectors are required to state whether or not

they are frost protected and to what level (temperature) they are protected. The freezing tests identified two

key issues, the first related to a frost protected system failing a freeze test while the second is that all systems

lost significant amounts of energy during the freeze test but the ‘energy saving’ computer model only

assumes that some systems lose energy – resulting in overstated energy savings for cold areas.


Other issues identified were that a manufacturer’s claim of frost resistance is not always an accurate

indication of whether the system will be able to withstand freezing conditions. Three of the eight systems

tested were declared as frost protected and of these, one failed the freeze test. While only one system failing

does not immediately appear to be a serious problem, the implications consumers of systems failing will vary

and may be substantial. Failures in collectors will result in consumers needing to undertake warranty action

that will be a time burden but will hopefully mean they are not ‘out of pocket’. Failure in the pipes running

between collectors and tanks could have far worse results if the point of failure was in the roof space, water

could leak into the roof space and impact the ceiling and cause other damage.

One of the remaining five systems which did not declare frost protection passed the test – this should not be

seen as a ‘bad’ result, but as more of a bonus as one system may be able to cope with prolonged cold

conditions if installed in the wrong climate or if a unexpected and unusual cold weather event occurred.

However, this system expelled a significant amount of water in the process (220 litres over 6 freeze events).

Excessive water usage during frost conditions means that more water will need to be heated for the next day

and may be an issue where water is scarce such as drought areas or where rainwater is used. That said, this

system would not be expected to be found in frost prone areas.

Of additional interest during the freeze test is that all systems lost energy to varying degrees whether

successful at preventing damage due to freezing or not. The heat loss occurred whether the system used

water or a freeze-resistance glycol solution and regardless whether the systems were a thermosiphon or a

split system. It is worth noting that for the tests, the tanks of thermosiphons were also placed in the ‘freeze

chamber’ as these tanks are equally as exposed as the collectors to cold conditions. The tanks of split systems

were kept outside of the freeze chamber based on the assumption that such tanks normally have some degree

of shelter (walls, eaves etc.).

Instant gas boosters in solar water systems

Current tests for instantaneous gas systems (including SWH gas boosters) are based on a 15°C inlet water

temperature. This temperature doesn’t reflect actual operating conditions for SWHs where inlet water to the

gas heaters may have already been substantially heated by the solar collectors.

Four tests were performed on the instantaneous gas boosters supplied with SWHs to assess the boosters’

behaviour at various ‘real life’ inlet temperatures. One out of four boosters tested significantly overshot the

required water temperature when hot inlet water was used. This is an issue when small amounts of hot water

are needed as the overheated water is simply cooled by mixing with cold water – so energy has been wasted

which costs the consumer. This is less of an issue when large amounts of hot water are needed.

It should be noted that some instantaneous gas systems are designed to be used in SWHs and will avoid

overshooting issues. Additionally the use of such a booster can be far more efficient than an in-tank booster

as an un-boosted storage tank has more ‘space’ for capturing solar energy.

Performance in field trials

As well as conducting tested required by Standards (as above), SWHs were tested and monitored in a typical

domestic situation. These tests were carried out in Melbourne during the first four months of the year,

summer and autumn, characterised by warm to mild temperatures with some periods of cloud cover– a

situation where a SWH should generally perform well. In order to determine the extent of energy savings

from the SWHs, a conventional electric system was also subjected to these tests.

The testing covered three difference household scenarios:

• Scenario 1 – A household goes on holidays for an extended period and the water heater is left turned on i.e.

no hot water is used.

— Results showed that even with no hot water required by the household, one of the three SWHs used a

significant amount of energy due to regular activation of the heating element. This indicates that a

significant amount of heat lost occurred from the idle system despite relative mild weather conditions.

This finding is also relevant for households with small hot water usage patterns.

• Scenario 2 – normal operating conditions for a typical household - boosting element may turn on as

required to meet the hot water demands.


— Results showed that one of the three SWHs used a significant amount of energy compared to the

reference electric system; i.e. it only provided 11% energy savings in favourable conditions. The other

systems offered savings of 52 to 65% which is again worse than what the ‘energy savings’ model

predicted for the actual conditions experienced.

• Scenario 3 –An energy conscious household that has the booster turned off and only uses water that has

been heated by the sun. The household will stop using hot water when the temperature at the outlet has

dropped below 45°C because of insufficient solar heating.

— Results showed that the amount of heated water delivered was more related to the size of the storage

tank than then ratio of collector area to tank volume. The results demonstrate why choosing a SWH

can be difficult as it depends on variables such as a user wanting:

— the most cost effective system;

— a system that will use the least annual energy;

— a system that won’t use too much roof space; and/or

— a system that will need to work when installed in a partially shaded or non-north facing roof.

Other findings were the inability for consumers to identify a poorly performing system because the electricity

or gas consumption were not separately reported on energy bills and the lack of post-installation assistance

available from the installer, the manufacturer or government consumer authorities to fix or replace a SWH

with substandard performance.

Impact of pipe work and booster type

Computer modelling for the amount of energy used was carried out for the electric boosted SWHs to

determine their sensitivity to changes in insulation thickness, pipe length between the tank and collector and

method of supplementary boosting.

The length of pipes between the storage tank and solar collector had a greater effect on the energy savings of

split systems than changes in pipe insulation thickness. Shorter pipe lengths between solar collectors and

tank gave three times more energy savings than those achieved with thicker pipe insulation. This result

indicated that it is important that installers and consumers are aware of these sensitivities when choosing a

location for their SWH and the associate solar collector(s).

Additionally, the level of ‘energy savings’ from different boosting methods were modelled for two split system

SWH. The results may be of use in informing consumers and sellers of SWHs about the most effective way to

boost a SWH in a particular climate area.

For all boosting methods, energy savings were highest in the warmer climate zones which indicates strong

suitability for SWHs in such areas. For a system with a small storage tank, in-line gas boosting offered the

highest (best) energy savings in all climate zones. For a system with a large tank, off-peak electric boosting

provided the most energy savings. Of particular interest was the noticeable change in energy savings offered

by in-line gas boosting which was less than that offered by manual or continuous electric boosting in

temperate climate zones and higher in cooler climate zones.

Testing ‘energy savings’ claims

The annual energy savings for the tested SWHs were calculated using the recognised modelling software. The

model inputs used were the results obtained from the independent E3 tests rather than manufacturer

supplied inputs.

Results showed that approximately half of the systems have very similar modelled and claimed energy

savings results. For the rest of the systems, there were substantial differences between the independent test

results and claimed energy savings. This may mean that manufacturers making reasonable claims are losing

sales to manufacturers who are making claims that were not substantiated by the E3 tests. This could mean

that many purchasers of SWH are relying on inaccurate claims. See Appendix 4 for table of modelled energy

savings.

Most of the systems had either equal to or greater than 60% energy savings in the ‘average’ climate zone,

used by the Clean Energy Regulator in Australia as a benchmark for receiving subsidies.


In New Zealand, SWHs wanting to qualify for ENERGY STAR must have an energy savings equal to or

greater than 70%. None of the systems tested registered energy savings of 70% in the New Zealand climate

conditions although the systems were Australian systems and subject to Australian-specific assumptions

such as hot water usage – so the results cannot be directly compared. However, while New Zealand is

generally colder than Australia and receives less solar energy, New Zealand SWHs carry claims of 70% to

87% energy savings. Indeed a 2012 New Zealand Parliamentary Report suggested that an optimal system

would provide 50 to 65% energy savings which indicates that over-claiming of performance is present in both

Australia and New Zealand.

Compliance, auditing and checking

There are no regulations that require the energy efficiency claims of SWH’s sold in Australia and

New Zealand to be tested to a common standard, to carry labels indicating their energy efficiency or to meet

any minimum prescribed levels of energy efficiency or performance. There is auditing of manufacturer and

supplier inputs by the Clean Energy Regulator but there is no full independent testing or associated

compliance in Australia or New Zealand.

There is one energy efficiency requirement for the gas components used with gas boosted SWHs.

Conclusions

A number of issues related to SWH performance and energy efficiency have been identified in this product

profile. In light of these issues it is worth considering if any changes to the SWH market could deliver better

outcomes. The key issues raised in this product profile include:

1. Claimed ‘energy savings’ are overall higher than independent test results using the defined industry

endorsed method;

2. Inability of consumers to select an appropriate water heater due to lack of accurate and comparative

information;

3. Potentially poor SWH performance in cold climates (not captured in Standards); and

4. Weak compliance with component-based and installation requirements.

Possible policy options

The E3 Committee is not seeking to advocate any particular policy option (or even a change from current

arrangements), but is seeking feedback from stakeholders on the costs, benefits and opportunities associated

with options presented to address energy efficiency and related performance issues. We also welcome

stakeholders proposing any alternative options. Many of the options provided to inform feedback would have

similar results so if one option was supported, many others may become redundant.

Stakeholder feedback is essential to help identify if the issues actually exist, whether they matter and if so,

what responses may be feasible and useful and who may implement them.

A detailed discussion on the policy options and their related benefits and costs are at Appendix 6.

Where to from here?

This consultation document is an investigation of the energy efficiency and market for SWHs.

Readers are asked to comment on a number of aspects in this document. While we welcome comments on all

aspects of this document, responses to the key questions following would be of particular assistance. Readers

also may wish to note that separate documents investigating the system performance of Heat Pump Water

Heaters and Electric Storage Water Heaters have been released under the E3 program. Consultation has

already occurred for these documents and they can be accessed at the Energy Rating water heating website.

Written comments should be sent via e-mail, and should be received by 26th September 2014. Comments can

be sent to:

Email: [email protected] Subject: Solar water heater product profile

http://www.energyrating.gov.au/products-themes/water-heating/

mailto:[email protected]


Guiding questions for stakeholder submission

The guiding questions have been provided to assist the E3 Committee to obtain stakeholder views and fill

information gaps. Stakeholder submissions are not limited to the following questions. The material in this

document, as well as written submissions and any additional information or views, will be considered in

helping governments to consider the scale of any shortcoming in the solar water heater market and the

desirability for any changes.

Solar water heater product profile – general questions

1. What, in your view are the contributing factors that make SWH technologies an important hot water

technology (e.g. reduce energy costs, energy consumption and associated emissions)?

2. What information do you think is adequate to inform a SWH purchase (size of tank, efficiency of

collectors, cost to run, energy savings, emissions levels, information relevant to a climate, suitability

to a climate, suitability to a dwelling, ability to compare different brands, ability to compare with

other water heater technologies etc.)?

3. Do you think the current information on expected ‘energy savings’ is important to purchasers (e.g.

claims that a SWH may save 60% energy etc.)?

4. Do you think overstating expected ‘energy savings’ by some manufacturers as (indicated by

independent testing) is a problem?

5. Do you think that the ‘energy savings’ model not being accurate for installations in the field

(especially for SWH in cold areas) is a problem?

6. Do you have any related concerns or issues you would like to raise?

7. Do you see a need for ENERGY STAR endorsement labelling of SWH’s in New Zealand?

8. Do you think EECA should revise the ENERGY STAR specification if any standards are changed?

Solar water heater product profile – detailed questions

Scope and performance

9. What aspects of SWH performance do you think are important (e.g. cost, efficiency, reheat time,

ability to operate in a range of climates, service life, etc.)? Please name the top five from most to least

important.

10. Is the degree of compliance with existing Standards adequate to provide a purchaser assurances

about acceptable performance?

11. Are there any barriers or impediments to either more sales of SWH or to higher performance levels?

Market

12. Do you agree with the market data presented for Australia and New Zealand? If not, can you provide

better data?

13. In particular, do you have any insights into more recent sales trends (either number of sales or types

of systems being favoured)?

14. Do you agree with the overall projected market trends? Are there any major trends or drivers that are

not specified in the product profile for Australia and/or New Zealand? Please provide information

you may have to support your opinion.

15. Do you agree with the breakdown of sales between the various product types? If not, can you provide

better data?

Information or labelling

16. Do you think there is a need for standardised SWH information or standard information across all

hot water heaters? Are there any other key information shortcomings that are affecting the efficiency

of the water heater market that are worth investigating?

17. Should standardised information also be placed in a central location to enable consumers and

business to compare such information? If so, who should be responsible for managing such a

database (e.g. industry group or government)?

18. Do you think there is a case for the physical labelling of SWHs or for all water heaters?


19. What impact do you think standardised information or labelling would have on competition, product

costs and consumer choice?

Standards – energy savings model (AS/NZS4234)

20. Are you concerned that (if testing is reflective of the broader market) around half of manufacturers

may be overstating their SWH performance using the current ‘energy savings’ computer model? Is

there a role for industry-based or government based checking of claims by random physical testing?

21. Are you concerned that the current model did not adequately assess the results of the real-life

physical testing? Can you propose any improvements? Alternatively, if you are not concerned about

the accuracy of the model can you please outline your reasons. Is it still a useful comparison tool if

there are problems with how the energy savings results are being are presented to consumers?

22. If a number of fixes are made to the Standard to increase the accuracy of the energy consumption

levels of solar water heaters, do you support also looking at the energy consumption estimates for the

conventional technologies, used as a point of comparison, which appear understated? This action, by

itself, will increase the claimed energy savings of both heat pump and solar water heaters.

23. The freeze testing showed that all systems lose energy in frost conditions despite the ‘energy savings’

model ‘exempting’ many systems. What do you think is the likely magnitude of these issues on actual

performance? Can you propose any improvements to either the Standard or how such information

should be communicated to consumers/installers?

24. The model appears to not accurately capture energy lost via expansion losses, heat losses from the

collectors and the relationship between temperature and tank heat losses. All these have implications

for the amount of ‘purchased’ energy that needs to be added, especially in colder conditions. Is this

correct, and what do you think is the likely magnitude of these issues on actual performance? Can

you propose any improvements to either the Standard or how such information should be

communicated to consumers/installers?

Standards –non-compliant products

25. Are you concerned about products failing independent freeze tests and collector impact resistance

tests? If so, what should be done?

26. If a standard is to set a minimum level of acceptability, is there a case to have two collector impact

resistance tests (ice ball or steel ball) without any associated marking for installers or consumers to

differentiate products?

Other energy efficiency options

27. Do you think that there is a case for minimum energy performance standards (MEPS) for SWH? If so

should MEPS focus on overall system performance (comprehensive) or component performance

(cheaper but may have more unintended consequences)?

28. If a system-based MEPS is preferable to a component approach, what type of test procedure would

you suggest for a MEPS (e.g. simple component calculations, physical system test, simulation etc.)?

29. Are there other options to facilitate energy efficiency for SWHs that should be considered?

30. Are there any other issues you are aware of that affect energy efficiency and performance of SWHs

that have not been discussed? Please provide as much detail as possible.

Manufacturers

Please look at Appendix 5 for details of solar water heater brands sold in Australia and New Zealand and

further questions related specifically to manufacturers

In providing comments, the E3 Committee would appreciate receiving as much data you can provide to

substantial your comments.


This chapter notes the scope of the project and describes what a solar water heater (SWH) is and how it

works.

A SWH uses energy from the sun to heat water. SWHs heat water through the absorption of solar energy,

which is converted to thermal energy to heat the water, and store the hot water for later use. SWHs generally

also have a booster, which uses an alternative source of energy for times when there is insufficient energy

from the sun to heat the water to the required temperature. When correctly installed and operated, SWHs are

highly efficient, as they are able to produce much more useful thermal energy than the purchased energy they

consume. SWHs are used in homes, businesses and industry.

This product profile covers SWHs that have a capacity up to and including 700L. This scope has been chosen

to align with the current Australian/New Zealand Standard (AS/NZS) 2712, as well as numerous past and

present government rebate programs and information initiatives. This means that larger commercial systems

have not been studied as part of this project. Additionally the scope of AS/NZS 2712 does not cover the

approach of directly connecting solar photovoltaic panels to an electric storage tank to heat water with the

electricity generated. This latter approach is uncommon but is now being marketed in Australia and

New Zealand. However, much of the information within this product profile will still be relevant to these

SWHs and to the broader hot water market.

Types of systems

There are two main types of solar water heating systems:

• Thermosiphon (close-coupled)

— A system in which the storage tank is mounted directly adjacent to the collector

• Split system

— The storage tank is located separate to the collector, generally on the ground.

Less common systems include:

• Systems with solid fuel boosting. These are also called wetback systems;

• Thermosiphon systems with the storage tank inside the roof instead of on the roof;

• Pre heat systems where a solar storage tank may be connected to an existing water heater to provide

preliminary heating of the water; and

• Retrofit split systems, which are most commonly existing conventional electric water heaters, with

solar collectors connected.

Close-coupled thermosiphon

Close-coupled thermosiphon is the most common solar water heating system on the market. It consists of

roof-mounted solar collectors combined with a horizontally mounted storage tank located immediately above

the collectors. In these systems, a pump is not required. Heated fluid rises naturally through the solar

collectors and enters the storage tank. When this happens, cooler water at the base of the storage tank is

forced out and flows down to the bottom of the collectors to be heated (see Figure 1).

Many commercially available solar water heaters use this method of heating, commonly referred to as

‘thermosiphon flow’.

1. Solar water heaters


Figure 1: Close-coupled thermosiphon

Source: Department of Industry

Split systems (or pumped systems)

A split system has the tank located below the level of the collectors, usually at ground level. Water must

therefore be pumped from the tank to the collectors and back by a thermostatically controlled pump (see

Figure 2).

Figure 2: Split system

Source: Department of Industry

SWHs can transfer heat directly to water or use a heat exchange fluid (water or otherwise) for heat transfer

between the solar collector and storage tank. These different approaches to heating the stored water are

known as open circuit or closed circuit, respectively.

• Open circuit

— Water flows through the primary circuit and is directly heated in the collector, then transferred

to the storage tank.

• Closed circuit

— Water is heated by a heat-transfer system that maintains a physical separation between the heat-

transfer fluid circulated in the collector and water in the storage tank.


System components

Solar collector

A solar collector is a device designed to absorb the sun’s radiant energy and transfer the thermal energy

gained to the fluid passing through the collector. The solar collectors are generally flat plates or evacuated

tubes.

• Flat plate: A solar collector that has a flat absorbing surface, with fluid passing through pipes within

the collector. Flat plate collectors operate at maximum efficiency when the sun is perpendicular to

the collector’s surface. Flat plates may require anti-freeze fluid or special drain-down procedures if

used in cold climates.

• Evacuated tube: A solar collector that has transparent tubing (usually glass), with an evacuated space

(or vacuum) between the tube wall and the absorber contained within the tube. The cylindrical tubes

allow incoming solar rays to be perpendicular to the collector’s surface when coming from many

directions, which assists solar absorption. There is a vacuum inside the tubes that reduces heat loss

and helps prevent freezing of the collectors. Individual tubes can be replaced if damaged rather than

replacing the whole collector.

Figure 3: Flat plate thermosiphon (left) and evacuated tube split system (right)

Storage tank

The storage tank is the vessel, including fittings, in which the heated water is stored. It may have a booster to

provide heating to supplement the solar input, together with a controller for the additional heating.

Storage tanks can be located on the roof, inside the roof cavity or on the ground, either inside or outside the

house.

Booster

A booster is a back-up heater that is used to heat water in the storage tank or as water is supplied to a

dwelling, when there is not sufficient solar contribution to heat the water to the desired temperature.

Boosters generally use either gas or electricity to heat the water.

• A gas booster may be located inside the hot water tank (storage or in-tank boost) or between the tank

and outlet (instantaneous).

• Electric boosted solar water heaters use an electric element to heat the water inside the storage tank1.

An in-tank boosting unit should ideally only activate when the water temperature is below the thermostat

setting and should turn off when the desired temperature is reached. For more control over the system, a

manual booster switch and/or a timer may be installed to maximise the solar contribution.

Pump

A circulation pump is required in split-systems, to circulate water between the storage tank and collector. A

circulation pump may operate during periods of solar gain to transfer energy from the collector to the storage

tank, but may also need to operate in cold conditions to help prevent damage from fluid freezing in the

collector and/or pipes. Thermosiphon systems don’t require circulation pumps, as they rely on the

thermosiphon principle to circulate water.

1 While instantaneous electric boosters exist, they were not widely used in SWHs at the time of this project.


System operation

SWHs generally have a booster to provide additional heating energy when there is not enough from the sun.

The type of booster and method of operation can affect system performance, running cost and energy

efficiency. The booster is the main way households can affect and control the operation of their SWH.

Electric boosted systems

Most electric boosted storage systems have one or two electric elements immersed in the storage tank. The

electric element in the storage tank is often located in the bottom half of the storage tank. This element

location results in the booster being used to heat up nearly all the water in the storage tank, which ensures

that more hot water is available. The element could also be located in the top half of the tank, which may help

to increase potential solar gain by using electrical energy to only heat water in the top half of the tank and

allow solar energy to heat water in the bottom of the tank.

Some electric boosted tanks have dual boosting elements, with one element located at the bottom of the tank

and one located in the top half of the tank. The bottom element is used as the main element to heat the water

in the tank and is generally run on cheaper off-peak electricity and the upper element in the top half or third

of the tank is the ‘back-up’ and is controlled to operate in times of high hot water demand.

The operation of elements can be controlled either manually, with a timer, or with a thermostat. If the

booster is operated manually, the user decides when to switch on and off the booster to best suit hot water

needs and/or tariff. Manual operation allows a user to increase boosting in periods of overcast or cold

weather and minimise energy use at other times. Use of a timer can also assist a user to control boosting to

take advantage of cheaper off-peak tariffs.

The thermostat controls the boosting element by switching it on when the water temperature drops to a set

temperature and off when the temperature the reaches thermostat settings (generally between 60°C-70°C).

Gas boosted systems

Gas boosted SWHs can be boosted either in-tank (storage system) or after the water leaves the storage tank

(instantaneous system), and use either natural gas or Liquefied Petroleum Gas (LPG). The booster is usually

controlled by thermostats but may also be manually operated.

In a gas storage system, boosting in the storage tank occurs by means of a burner that is thermostatically

controlled similar to an electric boosted system. Alternatively, gas boosting can be done instantaneously after

water has left the storage tank by an instantaneous booster fitted on or near the storage tank. The solar hot

water system is used to preheat the water before it flows through the instantaneous booster. The booster will

typically ignite when water below the required temperature flows through the unit with the amount of

boosting required depending on the temperature pre-heated water.


In both Australia and New Zealand, water heating is the second largest source of household energy use, after

space heating and cooling. In Australia, about 48% of the energy used for water heating comes from natural

gas, 45% from electricity, 3% from LPG and 4% from solar. In New Zealand, electricity supplies

approximately 76% of water heating energy, 21% from gas, approximately 2% from solar and less than 1%

other sources (ESWH consultation RIS; Gas water heater RIS; EECA, 2013).

Electricity is the most greenhouse intensive form of delivered energy in Australia, so while electricity

accounts for less than half of household water heating energy, it accounts for about 80% of the emissions

from water heating (GWA, 2009). In New Zealand, electricity accounts for about 75% of household water

heating energy, but is considerably less greenhouse gas intensive than in Australia, as nearly three quarters of

New Zealand’s electricity in 2010 was generated from renewable energy2. Household water heating currently

uses nearly 12% of all of New Zealand’s electricity (PCE, 2012).

The use of gas for water heating in Australia has been gradually increasing. In 2012, 49% of Australian

households used some form of gas for water heating (BIS Shrapnel, 2012). About 8% of New Zealand

households heat water using gas, mostly in the North Island where reticulated gas is available (PCE, 2012).

Energy consumption characteristics

Energy savings compared to conventional water heaters

The main advantage of a SWH compared with a conventional water heater is its potential to supply more

heat energy than the electrical or gas energy it consumes. A properly designed and installed SWH should use

at least 50% less electricity/gas in actual operation than a water heater that uses conventional electric

resistance or gas heating to supply the same amount of hot water. This amount will vary over the year,

dependent on weather conditions and patterns of hot water use. A reduction in electricity or gas use will

result in lower running costs and greenhouse gas emissions.

Energy use varies significantly by climate zone for SWHs and climates with low solar availability use a higher

proportion of conventional energy (GWA, 2007). When registering a SWH for Small-scale Technology

Certificate (STC) eligibility under the Small-scale Renewable Energy Scheme in Australia, a minimum energy

savings of 60% (relative to a conventional water heater of same boost fuel type and ‘load’) in climate zone 3

(Sydney) should be achieved.

In New Zealand, SWHs must achieve at least a 70% energy saving when compared to a reference

conventional electric resistance water heater in climate zone 5 (North Island and half of the South Island) to

be registered with the ENERGY STAR program and carry the ENERGY STAR label. The calculated

performance of an optimal SWH installation shows that in New Zealand, approximately 70% energy savings

should occur. However, when SWHs are designed and set up to achieve greater than 70% annual energy

savings there is a risk that they may over-heat in summer (Carrington, 2011).

In real-life New Zealand installations, the actual percentage of energy provided by the sun is more likely to be

50 to 65% of the energy required for water heating on average over the year (PCE, 2012). SWHs installed on

New Zealand’s South Island achieve approximately 14% less annual energy savings than those installed on

the North Island, due to lower solar irradiance and colder temperatures (Carrington, 2011).

2 The average emissions intensity of electricity supply in Australia in 2010 was 295 kg CO2-e/GJ, and natural gas 58 kg CO2-e/GJ

(GWA 2010). The average emissions intensity of electricity supply in New Zealand in 2010 was 38 kg CO2-e/GJ, and natural gas 54 kg

CO2-e/GJ (EECA 2012).

2. Energy use and greenhouse gas

emissions characteristics


Drivers of SWH energy consumption

The sources of energy consumption for SWHs can include boosting, operating a circulation pump, a

controller and a gas pilot light. This energy consumption can occur in response to low solar contribution,

high hot water demand, protection from freezing and for reheating water from tank, collector and pipe heat

losses.

One of the main drivers for the energy consumption of SWHs is the hot water use patterns of a household.

Households with high levels of hot water use will use the booster more often, and may require a larger

storage tank to ensure a reliable supply of hot water. Energy savings can be made through implementing

water saving actions or devices, such as shorter showers or low-flow showerheads. Combining a lower hot

water use with optimal installation, location and operation of the SWH can result in very low energy

consumption by the SWH.

The efficiency range for SWHs is much wider than the efficiency range of conventional water heaters, and is

sensitive to many factors including delivery, draw-off, collector efficiency etc. For conventional water heaters,

as the amount of water being delivered increases, task efficiency gradually increases (as the ‘sunk cost’ of

energy being lost from the tank decreases as a percentage of total energy use). For SWHs on the other hand,

as the amount of water being delivered increases, the task efficiency decreases, due to a higher reliance on

electricity or gas boosting.

Generally most energy is used by boosting which is usually highly seasonal, with solar energy often being

lowest when hot water demand is highest and vice versa, which can lead to a seasonal mismatch in demand

and supply (CLASP, 2011). This is shown in Figure 4, which is based on a New Zealand household (average

for six cities) that uses a ‘medium’ amount of hot water (PCE, 2012).

Figure 4: Energy profile of a solar water heater

Source: PCE, 2012

The lower green area shows the solar energy used in heating water and the grey area shows the electricity

used in heating water. It shows that the amount of solar energy used for heating water is highest in summer

and lowest in winter when hot water needs are the highest. The size of the seasonal difference is less in

warmer, sunnier cities.

More energy is required in total to heat water in winter, as inlet water to the storage tank is colder while hot

water usage and heat losses are higher.


Energy costs

Energy prices can have a large impact on the sales of SWHs. High, or increasing, energy prices can stimulate

consumers to look at water heating options that have low running costs and use less electricity/gas, to reduce

energy costs and protect against future price rises. However, this may be limited by lack of awareness of the

large proportion of household energy costs required for water heating.

Cost of living

An Australian senate committee on electricity prices held in 2012 discussed ways to reduce household

electricity consumption and energy bills. One of the main measures discussed was energy efficiency and

energy efficient appliances, such as water heaters. Evidence presented to the committee shows that energy

efficiency is the best option for cheaply reducing energy bills and greenhouse gas emissions.

Several organisations have highlighted how low-income and vulnerable households often have cheap,

inefficient appliances that result in high energy costs, due to a lack of information about efficient appliances

and the inability to afford high capital costs. A 2013 Australian Council of Social Service (ACOSS) report

emphasises that low-income households are exposed to numerous market failures that prevent access to

energy efficiency.

Electricity

There has been a recent decrease in electricity demand in Australia, which is likely to have been influenced by

a combination of building and appliance energy efficiency, higher rates of renewable energy (such as rooftop

solar photovoltaic (PV) generation and households and businesses changing in response to higher prices.

Green Energy Markets has estimated that solar PV and solar water heating, supported by the Australian

Renewable Energy Target (RET) and energy efficiency schemes, accounted for 53% of the reduction in

Australian energy demand between 2008 and 2012. SWHs may help to moderate wholesale electricity prices,

through decreasing demand for electricity (AEMC, 2012).

In New Zealand, electricity demand has decreased due to a number of factors such as higher electricity prices

and energy efficiency programs.

Figure 5: Electricity consumption in New Zealand

Source: EA, NZIER, ENA Analysis, PwC Analysis; EECA 2014

Note: Real GDP and electricity consumption are 12 month rolling averages


Residential electricity prices in Australia rose nationally over the past five years by 91% but have recently

stabilised while New Zealand prices are forecast to slowly rise over the foreseeable future (Figure 7 and

Figure 7).

Figure 6: Residential electricity price movements in Australia - 2011/12 to 2014/15

Source: AEMC, 2013

Note: These figures are based on average tariffs. Many jurisdictions have either specific hot water tariffs or more general off-peak tariffs that can be used for water heating.

Figure 7: New Zealand residential electricity price forecast to 2040

Source: EECA, 2013

Gas

The gas markets in eastern and western Australia are significantly different, due to different influencing

factors. Domestic gas prices in WA are influenced by international energy market conditions, whereas those

in eastern Australia traditionally haven’t been. Australia’s east coast has had relatively low gas prices by

international standards, as they have not been strongly influenced by international gas prices, however they


are predicted to increase. The Bureau of Resources and Energy Economics has predicted that eastern

Australia’s gas wholesale prices will converge towards global prices in anticipation of LNG exports from

2014−15 (AER, 2012). Domestic gas prices will also be influenced by many low-priced long-term contracts

coming to an end. New contracts will likely include higher prices (AEMC, 2012).

Figure 8: Average household gas bills by state

Source: Grattan Institute, 2013

Note: NSW values include data for the ACT

Residential gas prices in Australia rose over the past five years by 62% (AER, 2012). Victoria, which uses

most of the national residential gas consumption (Grattan Institute, 2013), has an average residential gas

price of $21.79/GJ in 2011/12 (ESC, 2012). As a comparison, the average residential price in WA is

$38.04/GJ (WA Department of Finance, 2013).

Domestic consumption of natural gas in New Zealand is limited to the North Island, where the production of

natural gas occurs. In 2013, the cost for residential natural gas in New Zealand was NZ$35.98/GJ (MBIE)

(Figure 9).

Figure 9: New Zealand residential gas price forecast to 2040

Source: EECA, 2013


Energy tariffs

A tariff is the amount charged to consumers for providing energy – it includes both fixed (supply) and

variable (usage) charges. Tariffs can vary depending on which state/territory you live in and your energy

distributor.

Electric boosted SWHs are often connected to an off-peak tariff to reduce water heating costs, as off-peak

tariffs are generally cheaper than continuous tariffs. A 2012 household survey by BIS Shrapnel shows that in

Australia, three quarters of those who use electricity for water heating are connected to an off-peak tariff,

except for Western Australia, where only 9% were connected to off-peak.

Peak demand

Energy networks are designed to have sufficient capacity to meet peak demand, which typically occurs on

days of extreme weather. Around 20−30% of Australia’s National Electricity Market’s (NEM) electricity

network capacity is not used 99% of the time. Peak capacity is drawn on for less than 90 hours a year, but the

associated network charges are fully passed on to retail energy customers (AER, 2012).

SWHs can help to address the issue of peak power and reduce peak demand, especially in Australia, where

peak electricity demand often occurs during hot summer days, when there is most sun available for heating

water.

Winter peak are also evident in areas such as Tasmania and New Zealand where there is a high demand for

heating with little solar contribution.

However, SWHs only have a marginal impact on annual electricity demand in New Zealand. SWHs require

the greatest amount of electricity in winter, when there is less solar energy, and when overall electricity

demand is highest (PCE, 2012).


Australia and New Zealand have separate energy efficiency strategies; the National Strategy on Energy

Efficiency (NSEE) in Australia and the New Zealand Energy Efficiency and Conservation Strategy (NZEECS).

These strategies note the substantial reductions in energy use and greenhouse gas emissions that can be

made by improving the efficiency of appliances, such as water heaters.

Australia

The Council of Australian Governments (COAG) first agreed to the NSEE in 2009, with a revision in 2010.

The Strategy was designed to substantially improve minimum standards for energy efficiency and accelerate

the introduction of new technologies through improving regulatory processes and addressing the barriers to

the uptake of new energy efficient products and technologies. The NSEE includes the National Hot Water

Strategic Framework (NHWSF) which aims to improve the efficiency and emissions of water heating.

New Zealand

The government’s direction for the energy sector is outlined in the New Zealand Energy Strategy 2011-20213.

‘Achieving efficient use of energy’ is one of the priorities of the Energy Strategy, and this requires ‘better

consumer information to inform energy choices’.

The New Zealand Energy Efficiency and Conservation Strategy 2011-2016 (NZEECS) is a companion to the

Energy Strategy and is the second five-year strategy under the Energy Efficiency and Conservation Act 2000.

The objective of the NZEECS for products is to improve consumer uptake of energy efficient products,

including through robust economic analysis of energy labelling and Minimum Energy Performance

Standards in partnership with Australia.

Regulations and regulators

Australia

Greenhouse and Energy Minimum Standards

The Greenhouse and Energy Minimum Standards (GEMS) Act 2012 came into effect on 1 October 2012. It is

national legislation that regulates equipment energy efficiency in Australia and replaced multiple

jurisdictional regulation and regulators – a significant reduction in regulatory burden.

The Australian GEMS Regulator is responsible for registering products and administering the legislation in

Australia4.

There is an energy efficiency standard that is applied to the gas booster for all gas water heaters including

gas-boosted SWHs. See Appendix 1 for more detail on this standard.

Clean Energy Regulator

The Clean Energy Regulator (CER) is the Government body responsible for administering activities as part of

the RET. The Small-scale Renewable Energy Scheme (SRES) is one part of the RET, and creates a financial

incentive for owners to install eligible small-scale installations such as solar water heaters, heat pumps or

solar panel systems. Small-scale technology certificates (STCs) are used to provide the financial incentive and

the number of STCs created for each eligible installation is dependent on the amount of electricity produced

or displaced. A Green Energy Markets suggests that the number of SWHs that create STCs covers 85 to 90%

of the total number of SWHs sold.

3 More information on the New Zealand Energy Strategy is available from: www.med.govt.nz/sectors-industries/energy/strategies 4 More information is available from: www.energyrating.gov.au/programs/e3-program/meps/about/

3. Government/policy context

http://ret.cleanenergyregulator.gov.au/

http://ret.cleanenergyregulator.gov.au/Hot-Water-Systems/hot-water-systems

http://ret.cleanenergyregulator.gov.au/Solar-Panels/solar-panels

http://www.med.govt.nz/sectors-industries/energy/strategies

http://www.energyrating.gov.au/programs/e3program/meps/about/


It is important to note that the focus of the STC framework on energy displacement/generation is very

different to the focus of the E3 committee on energy efficiency. For example, the potential for a SWH to

displace energy can be increased by increasing the volume of the storage tank, although the effect an

increased tank size has on energy efficiency is uncertain. It is not clear what effect the SRES has had on

efficiency levels, although it has been successful in its goal to increase the amount of renewable energy being

produced.

Several regulations and energy efficiency programs operated by the state, territory and federal governments,

such as the National Construction Code, use STC numbers as a proxy for energy efficiency of SWHs.

New Zealand

The Energy Efficiency and Conservation Authority (EECA) is a New Zealand Government body that

administers voluntary labelling for SWHs, as part of the ENERGY STAR program. For SWHs to qualify for

ENERGY STAR, the energy savings must be at least 70% greater than an electric water heater in climate zone

5 (most of New Zealand). ENERGY STAR models are listed on EECA’s ENERGYWISE website to enable

customers to choose an energy saving SWH model. ENERGY STAR does not provide a compliance program.

The ENERGY STAR specification is for packaged systems and doesn’t apply to retrofit SWHs. SWHs that

either don’t meet or don’t wish to register with ENERGY STAR and EECA may still be sold.

Equipment Energy Efficiency Program

The Equipment Energy Efficiency (E3) Program is a joint initiative of the Australian Commonwealth, State

and Territory governments and the New Zealand Government. The coordination of appliance energy

efficiency efforts across Australia and New Zealand such as mandatory Minimum Energy Performance

Standards (MEPS), mandatory Energy Rating Labels is conducted through national legislation (the

Greenhouse and Energy Minimum Standards (GEMS) Act 2012) on behalf of E3.

The work of E3 is guided by Measure 2 of the NSEE, which is ‘Reducing impediments to the uptake of energy

efficiency’. Improving the efficiency of hot water appliances contributes to the objectives of E3 and the

previously mentioned Australian and New Zealand energy strategies.

Standards

Australian and/or New Zealand Standards are one of the tools available to E3 to test appliances and assess if

they meet energy efficiency standards and /or the claims being made by manufacturers. MEPS or labelling

requirements are introduced into law as Determinations using the GEMS Act 2012. There are a number of

Australian and/or New Zealand standards that are either directly or indirectly relevant to SWHs. These

standards cover things like SWH construction, performance, energy consumption and test methods.

SWHs or their components are not currently covered by MEPS, with the exception of gas boosted SWHs.

Electric boosted SWHs are currently provided an exemption to the tank heat loss requirements that other

electric storage tanks must meet.

More detail on Australian/New Zealand and international standards can be found in Appendix 1.

Building codes

Australia

All Australian states and territories other than Tasmania, Queensland and the Northern Territory have rules

restricting the use of greenhouse gas intensive water heaters in new Class 1 buildings (i.e. detached, terrace,

row and town houses), either through their own building regulations or by reference to the relevant clauses in

the National Construction Code (NCC). These rules have largely eliminated conventional electric resistance

water heaters from the new home market in these jurisdictions in favour of heat pumps, solar, natural gas

and LPG water heaters.


National Construction Code 2011

The NCC is a COAG initiative developed to incorporate the Building Code of Australia (BCA) and the

Plumbing Code of Australia into a single code. Volumes 1 and 2 make up the Building Code and cover the

regulations and requirements for installation of water heaters in new buildings.

The BCA also sets out regulations on the type of water heater that can be installed and what standard of

energy performance these water heaters must comply with. In general, the BCA supports the installation of

solar and heat pump water heaters compliant to minimum performance requirements, gas water heaters

rated not less than 5 stars and electric resistance water heaters of not more than 50 litres (requirements vary

by jurisdiction).

Victoria has had a 6 star standard for homes since 2011, which requires the installation of either a SWH or a

rainwater tank in new homes.

Other regulatory schemes

The BASIX rating scheme, introduced in New South Wales in 2004, allows the use of electric resistance water

heaters in new and existing buildings, but imposes such a high rating penalty that builders must compensate

with much stricter levels of ‘thermal performance’ or more energy efficient lighting or fixed appliances.

BASIX has resulted in an increase in the SWH share of the NSW water heater market, to about 26% of new

homes built from 2005 to 2008 (BASIX 2011).

Existing buildings

The NCC does not apply to water heater installations in existing buildings – each state and territory has its

own requirements, which are often covered in the state or territory’s plumbing code.

South Australia and Queensland have had regulations (metropolitan and nearby areas for SA and gas

reticulated areas for Qld) restricting the replacement of electric resistance water heaters since 2008 and 2010

respectively. Since February 2013, Qld no longer has regulations restricting the replacement of electric

resistance water heaters and in SA, the water heater installation requirements were changed in January

20145.

New Zealand

All new building work in New Zealand must comply with the New Zealand Building Code (NZBC), which is

the first schedule to the Building Regulations 1992. It has since been reviewed to align it with the Building

Act 2004. The NZBC is a performance-based code, and states how a building and its components must

perform as opposed to describing how the building must be designed and constructed.

Building consent must be obtained for the installation of a water heater in both new and existing buildings.

However, the Building Act 2004 may change in the near future, with discussion on the building consent no

longer being required for SWHs.

A building consent is the formal approval, under the New Zealand Building Act, for an applicant to undertake

building work. Building work includes the installation of a SWH, as well as the retrofit of an existing water

heater. An application for a building consent must be made to a building consent authority that is authorised

to grant a building consent for the proposed building work.

Building consents for SWHs can cost up to $500, even with the solar subsidy provided by some councils.

There are also many forms that must be submitted when applying for a building consent, with decisions on

whether to grant or refuse a building consent application generally required within 20 working days from the

date the application is received.

New construction

The NZBC has requirements for SWHs including installation, durability (15 years) and energy efficiency (the

tank must meet AS/NZS 4692.2:2005)6.

5 More information is available from http://www.sa.gov.au 6 More information is available from http://www.dbh.govt.nz

http://www.dbh.govt.nz/UserFiles/File/Publications/Building/Guidance-information/pdf/technical-guidance-solar-water-heating-guidance-document.pdf


The Energy Efficiency Compliance Document of the NZBC sets out the energy efficiency requirements for

systems that heat, store, or distribute hot water to and from sanitary fixtures or sanitary appliances.

The NZBC requires that hot water systems comply with NZS 4305 Energy efficiency – domestic type hot

water systems, which specifies maximum heat losses for all types of water heater, up to 700 litres capacity.

Rebates & incentives

There have been both State and Territory and Australian and New Zealand government rebates and

incentives for the purchase and installation of solar water heaters, however most have now closed. These

schemes were regarded as interim measures to support and promote the uptake of these new and emerging

products. Discussion of key rebate and incentives programs is at Appendix 2.


The water heater market is effectively segmented into two parts – purchases of new water heaters and

replacement water heaters in existing dwellings. The volume of sales for new homes is tied to the market for

new homes, which can be quite variable.

Marketing strategies, regulation and policy initiatives have affected these two segments of the market

differently. For example, sales of water heaters for the new home market segment have been affected by

building regulations requiring certain types of water heaters in new housing, and by rebates and incentives

for the installation of high efficiency water heaters in both new and existing housing.

The rate of water heater system replacement largely depends on the rate of system failure. In Australia in

2012, 70% of water heater sales were for the replacement of an existing system, 20% were for new houses and

6% were renovation-related (BIS Shrapnel, 2012).

Given the high value that householders place on continuing the availability of hot water, the decision around

replacing a failed hot water system is usually rushed, which limits the time available for research, selection

and installation. There is often a preference for the cheapest capital option even if it is known to have higher

lifetime costs, and the most common pattern of replacement is like for like (GWA, 2009).

Cost

The largest part of the cost involved with a SWH (usually over 90%) occurs at the time of purchase, as the

maintenance and running costs of a SWH are generally low (ESTIF, 2012b).

The capital cost of a solar water heater is generally significantly higher than the capital cost of other types of

water heaters, as shown in Table 2. The higher capital cost of SWHs can be a barrier to SWH uptake,

especially in the replacement market (Department of Manufacturing, Innovation, Trade, Resources and

Energy, 2012). The average cost for a SWH in Australia in 2012 was AU$3,070 (BIS Shrapnel, 2012), while

the average cost in New Zealand is NZ$7,000 (EECA estimate).

2008 2010 2012 % Change

2008 - 2012

Electric storage $1,300 $1,151 $1,105 -15%

Gas storage $1,300 $1,328 $1,255 -3%

Gas instant $1,350 $1,140 $1,378 +2%

Heat pump N/A $2,543 $1,904 N/A

Solar $3,700 $3,018 $3,070 -17%

Average $1,620 $1,814 $1,796 +11%

Table 1: Average capital cost in Australia (including installation) by water heater type, 2008-2012

Source: BIS Shrapnel, 2012

Note: While there have generally been price declines for all water heating technologies, the total average cost has increased. This is due to a shift to more expensive, but more efficient, technologies.

4. Market characteristics


Sales and stock

Australia

SWHs made up approximately 12% of the installed water heater stock in 2012, which has increased from 7%

in 2008. Of these, 77% of installed SWHs are electric boosted and 23% are gas boosted. Thermosiphons

made up 51% of the market in 2012, while split systems made up the remaining 49% of the market. The

Australian market is dominated by systems with flat plate collectors, with only 18% of collectors in 2012

being evacuated tubes (BIS Shrapnel, 2012).

The most important drivers influencing the sales of SWHs include:

• Capital cost comparative to other water heater types;

• Access to reticulated gas;

• Financial incentives and rebates;

• Regulations; and

• Consumer perceptions of energy prices (Green Energy Markets, 2013).

The estimated current stock and sales of water heaters in Australia is presented in Table 2. Electric storage

water heaters dominate the Australian household water heater stock, but gas water heaters dominate current

water heater sales.

2011 Stock 2012 Sales

Water heater type Australia Market share (%) Market share (%)

Electric storage 4,496,300 51 25

Mains gas 3,108,600 35 -

LPG/bottled gas 339,800 4 -

Gas total 3,448,400 39 43

Solar 729,000 8 26

Other (mainly heat pump) 196,000 2 7

Total 8,869,700

Table 2: Australian water heater stock and sales

Source: ABS, 2011; BIS Shrapnel, 2012

Type of water

heater

NSW VIC QLD SA WA Australia

Electric storage 49 16 61 21 8 36

Gas storage 20 52 7 24 37 27

Gas instant 15 20 12 40 28 19

Solar electric boost 9 3 14 8 16 9

Solar gas boost 1 5 1 3 6 3

Solar total 10 8 15 11 22 12

Heat pump 3 1 4 2 2 3

Electric instant 3 3 1 2 3 3

Table 3: Water heater stock in 2012, by state (%)


SWH installations peaked in Australia in 2009, with over 120,000 SWHs installed. As shown in Figure 10,

SWH installations have steadily declined since 2009, to approximately 55,000 installations in 2012. As at


July 2013, the data presented for 2012 will be an underestimate, as STC registrations are permitted up to 12

months after installation. CER data covers approximately 90% of SWH installations in Australia.

Figure 10: SWH installations by year and climate zone

Source: Clean Energy Regulator, 2013

The distribution of SWH installations in different climate zones has also changed in recent years. Since 2004,

installations in the colder areas of Australia (zone 4, Figure 10) have increased in number, and as a

percentage of overall installations (6% in 2004 to an estimated 35% in 2012).

One of the major drivers of the large increase in SWH installations that occurred from 2009 was the

availability of Commonwealth and state and territory government rebates. The subsequent ending of many

Government rebates and incentives would have also contributed to the recent decline in SWH installations.

Before the spike in SWH installations began in 2009, NSW, Qld and WA had the highest number of SWH

installations occurring (Figure 11). Between 2008 and 2011 installations substantially increased in NSW, Qld

and Vic. With recent declines in NSW and Qld installations, Vic is now installing the most SWHs.


Figure 11: SWH installations by year and state/territory7

Source: Clean Energy Regulator, 2013

The majority of SWH installations that occurred between 2008 and 2010 were to replace conventional

electric water heaters. However, in recent years new building constructions have been the main driver of

SWH installations (Figure 12) (Green Energy Markets, 2013).

Figure 12: Solar water heaters installed by market segment

Source: Green Energy Markets, 2013

New Zealand

Solar water heaters have a low market share in the New Zealand. Conventional electric water heaters are the

dominant water heating technology, although natural gas is common in parts of the North Island.

Approximately half of the SWHs in New Zealand have flat plates, with the other half having evacuated tubes.

Split systems are most common in the New Zealand water heater market, with the storage tank often located

inside the house so that it is not exposed to extreme winter temperatures. About half of the market uses

7 2012 data will be an underestimate, but relative trends by jurisdiction are still informative.


packaged systems (mostly split systems) and the other half uses retrofit systems (all of these are split

systems). Retrofit systems are where the solar collector is connected to an existing water tank.

EECA estimated in 2008 that only 1.6% of New Zealand home owners had a SWH. The estimated current

stock of water heaters in New Zealand is presented in Table 4.

Type New Zealand Market share (%)

Electric storage 1,225,000 76

Gas storage & instantaneous 340,000 21

Solar electric boost 31,000 2

Solar gas boost 9,000 0.6

Heat pump 2,500 0.2

Total 1,607,500

Table 4: Estimated 2012 New Zealand water heater stock

Source: ESWH Consultation RIS; Gas water heater RIS; EECA, 2013

Most New Zealand SWHs claim to achieve 70% energy savings in comparison to a reference conventional

electric water heater climate zone 58 when modelled to AS/NZS 4234, as evidenced by the large number of

SWHs that achieve the ENERGY STAR rating. About 170 ENERGY STAR models available in New Zealand

are listed, along with the supplier and system details, on the ENERGYWISE website9.

Figure 13: Solar and heat pump water heater installations in New Zealand between 2001 and 2012

Source: EECA, 2013

Figure 13 shows that SWH installations in New Zealand gradually increased from 2001 to 2007. There have

been two large spikes in SWH installations, from 2004 to 2007 and 2008 to 2012. These spikes occurred in

line with the availability of EECA grant funding for SWHs.

8 Note: NZ climate zone 5 in AS/NZS 4234 is different to the climate zone 5 used for the testing and modelling in this product profile. 9 The address for the ENERGYWISE website is: http://www.energywise.govt.nz/products/listing/102/solar-water

http://www.energywise.govt.nz/products/listing/102/solar-water


EECA estimates SWH sales are currently at approximately 2,500 to 3,500 per year in New Zealand, as seen

in Table 5 (EECA, 2013).

Type New Zealand Market share (%)

Electric storage 50,000 68

Gas storage & instantaneous 20,00010 27

Solar electric & gas boost 2,500-3,000 4

Heat pump 500 0.7

Total 73,000-73,500

Table 5: 2012 water heater sales in New Zealand

Source: ESWH RIS; Gas water heater RIS; EECA, 2013

Manufacturers and suppliers

There are a number of major suppliers in the Australian SWH market, including11:

• Dux (GWA Group Limited)

• Rheem (and its affiliate brands including Solahart, Aquamax and Edwards)

• Rinnai

• Bosch

At present, there are 86 brands and almost 7000 separate models of SWHs with a capacity up to and

including 700L registered with the Clean Energy Regulator as eligible for STCs. Table 6 shows that Solahart

dominates the SWH market, accounting for 31% of total SWH sales in Australia in 2012. Rheem accounts for

18% of SWH sales and Rinnai 12% (BIS Shrapnel 2012). It is estimated that the products of Rheem and its

affiliated brands constitute approximately 60% of total SWH sales.

Brand Percent of sales

2008 2010 2012

Solahart 44 38 31

Rheem - 15 18

Rinnai 2 7 12

Edwards 17 7 7

Dux 19 5 5

Aquamax - 3 3

Bosch - - 3

Kelvinator - - 1

Vulcan - - 1

Saxon - 1 -

Others 18 24 19

Table 6: Australian SWH market penetration by percent of sales and brand, 2008-12


10 Sales of gas storage water heaters are very low, this figure is mostly from gas instantaneous systems. 11 There are many other companies involved in the SWH market in Australia.


The New Zealand SWH market has five major players nationwide. Nova is the dominant company and other

major players include Solar City, Solar Group, Switch and Eco Solar. In 2013 there were estimated to be 24

brands of SWHs being sold (EECA).

Market trends

The factors that influence the annual sales of all water heaters are the replacement of existing water heaters,

construction of new homes, and significant house renovations that require replacement of the existing water

heater (GWA, 2009). The percentage of such sales that SWHs constitute are driven by a number of factors.

Australian market trends

There are a number of market drivers that have contributed to the increasing sales of SWHs in Australia.

Some of these drivers are expected to continue into the future. The main drivers identified are:

• Small-scale Renewable Energy Scheme (underpinned by the Renewable Energy Target);

• Financial incentives and rebates;

• Increasing energy prices; and

• Water heater and building regulations.

These drivers have contributed to the current market trends, which suggest that Australians are slowly

moving away from conventional electric water heaters towards high efficiency systems such as SWHs. The

spike in SWH installations in 2009 (Figure 10) also demonstrate the ability of rebates to drive the market.

Table 7 shows that since 2008, the market share of the older conventional electric water heater technology

has been declining with SWHs, heat pump water heaters and instant electric water heaters increasing their

market share as a consequence (BIS Shrapnel, 2012). It should be noted that both heat pumps and instant

electric water heaters were not commonly sold in Australia until recent times, so sale increases are from a

low base.

Type of water heater 2008 2010 2012 % Change in water

heater penetration

2008 – 2012

Electric storage 47 42 36 -23%

Gas storage 26 27 27 4%

Gas instant 19 16 19 0%

Solar total12 7 10 12 71%

Heat pump <0.5 3 3 500%

Electric instant <0.5 2 3 500%

Table 7: Water heater stock, by year (%)


New Zealand market trends

SWH sales have been increasing in New Zealand from a very low base, but have recently slowed. In 2012,

SWHs made up only about 3% of water heater stock in New Zealand (PCE, 2012). However, as shown in

Table 5, they made up 4% of water heater sales.

SWH sales have been slow since EECA grants were removed in 2012, however the market could grow if

building consents for the installation of SWHs are no longer required.

Promotion and government endorsement of SWHs through the ENERGYWISE program has contributed to

creating a market for SWHs in New Zealand. EECA’s ENERGYWISE program provided both SWH grants and

information for consumers. While the grant scheme has recently ended, the information provision

component of the ENERGYWISE program has continued.

12 Data was not available for solar separated into electric boost and gas boost by year.


Solar water heaters are relatively complex systems, so predicting their performance is not straightforward.

For any given model, factors including electricity/gas consumed, amount of hot water supplied and overall

energy efficiency can all vary, depending on the following:

• location and climate where it is installed;

• installation quality;

• temperature of incoming water;

• heat loss of the storage tank;

• heat loss of the collector;

• insulation of pipes;

• quantity of hot water drawn off each day;

• quantity, duration and time of day of each draw;

• time interval between draws;

• heating efficiency or coefficient of performance of the system;

• thermostat and control strategy settings; and

• energisation profile, e.g. whether the booster is on continuous, timer-based or manual operation.

SWHs are highly sensitive to climatic factors such as solar input, ambient air temperatures and cold water

temperatures (CLASP, 2011). SWHs are significantly affected by cold climates, and their efficiency,

performance, durability and lifespan can be negatively impacted, especially if a suitable system isn’t installed.

For households in colder climates, especially frost-prone areas, there are SWHs designed to withstand these

weather conditions. Frost protection is generally required in southern parts of Australia and most of

New Zealand. Having frost protection can increase the electricity/gas and or water usage in winter,

depending on the type of frost protection used.

Performance claims

Manufacturers and retailers provide information about many aspects of SWH performance and design in

marketing material for consumers, but the type of information provided and the way of presenting similar

claims varies by manufacturer and retailer.

Due to these differing claims, it can be difficult for consumers to verify claims, or use the information

provided to compare with other SWH products. Some claims may also be unclear or confusing for consumers

who don’t have a good understanding of how a SWH works. Additionally a study by the Institute for

Sustainable Futures found that ‘claims of SWH manufacturers can be shown to be exaggerated’, especially for

claimed energy savings and expected solar contribution levels.

An online search found that only a few manufacturers mentioned performance aspects such as hot water

delivery. If key performance characteristics are difficult or not possible to find, comparing systems to make a

fully informed purchasing decision may not be possible. However there are some aspects of SWH

performance or design that are difficult for a manufacturer to discuss simply in marketing material. For

example collector performance can be influenced by many factors, such as latitude of installation, collector

angle and orientation, climate, shading, and the distance from the storage tank. It is acknowledged that it is

difficult to provide accurate information on these factors and it may disadvantage a particular manufacturer

or retailer to provide this information if others do not provide similar information on collector performance

constraints.

In Australia, the only information that is consistently provided by manufacturers is the amount of STCs a

system is eligible for. This allows consumers to compare SWHs by STCs, but as STCs estimate potential

energy displacement rather than energy efficiency, this is not always an accurate and reliable method of

5. Product performance


comparing SWH performance or likely running cost. Large SWHs generally receive more STCs as they have

the potential to displace larger amounts of energy, but may be a poor choice for homes with low hot water

use.

In New Zealand, the ENERGY STAR label is a consistent source of information provided by manufacturers

and retailers for ENERGY STAR eligible SWHs. However, an ENERGY STAR label does not help a consumer

compare between SWHs that carry this endorsement, as specific energy savings levels are not presented on

the label. ENERGY STAR is based on the same method of estimating conventional energy displacement

(rather than energy efficiency) as STCs in Australia. Information on estimated energy savings for

ENERGY STAR SWHs are presented as additional performance information on the EECA website13. This

additional information has similar drawbacks to the Australian STC information, as the calculations are

based on an undisclosed level of hot water use that might not be relevant to a particular consumer.

13 http://www.eeca.govt.nz/products/listing/102/solar-water

http://www.eeca.govt.nz/products/listing/102/solar-water


Laboratory and field testing of SWHs was conducted to inform this product profile and provide information

and data on SWH performance and energy efficiency. It also allowed comparison with claims made by

manufacturers and informed the consideration of possible policy options. The aim of the testing was to

provide data illustrating component performance characteristics, drivers of performance and whole system

performance characteristics. It is important to note that the tests were not ‘check-testing’ compliance tests

and results have been discussed with relevant manufacturers.

Systems were chosen to ensure that a wide range of system, tank and component types were tested - eight

electric boosted and six gas boosted SWHs were tested. The tests performed included component testing in

line with existing standards, as well as system testing in the field.

Testing of electric boosted solar water heaters

Eight electric boosted SWHs were tested – five of these were split systems and three were thermosiphons.

Two systems had evacuated tube collectors and six had flat plate collectors. All collector tests were performed

with the collectors supplied with the electric boosted SWHs.

The following physical tests were performed for electric boosted SWHs:

• Standing heat loss from storage tanks and rated hot water delivery

• System heat loss

• Performance in the field

• Collector efficiency

• Collector damage tests – freezing and impact resistance

Testing of gas boosted solar water heaters

Six gas boosted SWHs were tested – three of these were split systems and three were thermosiphons. Four of

the systems were instantaneous and two were storage (in-tank boost) systems. Testing was done only on the

gas-specific components of the system, as other standard components such as collectors were tested as part

of testing the electric boosted systems.

The following physical tests were performed for gas boosted SWHs:

• Thermal efficiency and maintenance gas consumption

• Gas consumption

• Standing heat loss from storage tanks and rated hot water delivery

• Instantaneous gas booster performance

Tank test results

Standing heat loss from storage tanks

The aim of the standing heat loss test was to determine the thermal performance of a hot water storage tank

by monitoring the energy required by the unit to maintain a constant water temperature of 75oC at an

ambient air temperature of 20oC.

All storage tanks were tested to AS/NZS 4692.1. Gas boosted SWHs are not required to be tested against

AS/NZS 4692.1, and electric boosted SWHs have an exclusion from the Australian electric storage water

heater tank heat loss MEPS outlined in AS/NZS 4692.2. However, thermal performance of the storage tank is

a driver of system performance and a key element used by manufacturers when making energy savings

claims.

6. Solar water heater testing


Low heat loss from the storage tank is important when seeking to store water across periods of low solar gain.

Only two electric boosted and two gas boosted SWH tanks met the Australian tank heat loss requirements

that apply to conventional electric water heaters. Three of those that met the requirements were split systems

and one was a thermosiphon. Of the tanks that didn’t meet the MEPS requirements, most were within

0.5kWh. This can be considered an acceptable amount of heat loss, as SWH storage tanks typically have more

connection ports that are additional sources of heat loss than conventional storage tanks.

Figure 14 shows the standing heat loss results for both the gas and electric boosted storage tanks, when rated

against the current electric storage water heater tank heat loss MEPS, as outlined in AS/NZS 4692.2. An

additional figure is provided in Appendix 4 which adjusts the results due to unfavourable ‘rounding’ from

MEPS steps.

Figure 14: SWH tank heat loss compared to MEPS level for ESWHs

Hot water delivery

All eight of the electric boosted SWHs and six of the gas boosted SWHs were subject to hot water delivery

tests, as outlined in AS/NZS 4692.1. Hot water delivery is how much hot water can be drawn from the tank

before there is a 12oC drop in water temperature at the tank outlet. Not all SWHs have hot water delivery

declared on the tanks and may declare volume instead, which results in inconsistent information being

provided to consumers.

Table 8 and Table 9 show that split systems were able to provide a larger amount of hot water as a percentage

of the tank volume than thermosiphons. This may be useful information for a consumer when comparing

split systems with thermosiphons.


Model Measured

volume (L)

Measured hot

water delivery

(L)

Measured hot

water delivery /

Measured volume

Split systems

Model E1 (SE250) 251.2 243.3 97%

Model E2 (SF415) 416.9 405.8 97%

Model E3 (SF270) 269.1 248.9 92%

Model E4 (SF325) 326.3 311.7 96%

Model E5 (SE340) 339 325.2 96%

Thermosiphons

Model E6 (TF305) 289.5 244.8 85% Model E7 (TF330) 321.3 278.7 87%

Model E8 (TF300) 302.7 261.8 86% Table 8: Measured volume and hot water delivery for electric boosted systems

Model Measured volume (L)

Measured hot water delivery (L)

Measured hot water delivery / Measured volume

Thermosiphons

Model G1 (TI180) 178.3 157.6 88%

Model G2 (TI305) 296.9 252.2 85%

Model G6 (TS300) 291.5 266 91%

Split systems

Model G3 (SI165) 164.8 149 90%

Model G4 (SI215) 218.3 204.1 93%

Model G5 (SS322) 321.4 315.1 98%

Table 9: Measured volume and hot water delivery for gas boosted systems

System heat loss

The system heat loss test is not a test defined in current Australian/New Zealand standards, but was

conducted for three electric boosted systems to determine the heat loss of not only the storage tank, but the

whole system, including the collector and the pipes between the collector and the storage tank. Determining

the heat loss of the whole system helps indicate how much energy a system may lose in reality and indicate if

the practice of only measuring tank heat loss (for energy savings modelling and claims) is reasonable. The

test was based on the AS/NZS 4692.1 standing heat loss test, but modified to allow the whole system to be

tested. Both the thermosiphons and split systems were tested with the whole system inside the test chamber.

Figure 15 shows that system heat loss values were on average 0.48kWh/24 hours higher than tank heat loss

values at 20oC. The difference between system and tank heat loss was 17% for Model E1, 13% for Model E2

and 11% for Model E8. System heat loss is higher, as heat is lost not only from the storage tank, but also from

the solar collector and the pipes. As some of this additional heat loss may be countered by solar gain (rather

than using additional boosting), computer modelling was used and determined that the additional heat loss

was equivalent to around 2% energy savings or around $20 per year in additional energy costs – see

Appendix 4 for details.


Figure 15: System heat loss compared to tank heat loss at 20oC

Effect of air temperature on system heat loss

When determining the heat loss of a SWH and its associated annual energy savings, tank heat loss at an air

temperature of 20oC is the value that is used in AS/NZS 4692.1. However, as shown in the previous section,

to get a more accurate representation of heat loss from a SWH, heat loss from all components should be

considered to get an overall system heat loss value.

Standardising heat loss test conditions to 20oC helps to ensure that test results are consistent and can be

reproduced, but doesn’t take into account the fact that the majority of the Australian population and all of the

New Zealand population live in areas where the average annual temperature is less than 20⁰C (see Figure 16

and Figure 17).

Figure 16: Annual average daily mean temperature in Australia 1961-1990

Figure 17: Median annual average temperature in New Zealand


During winter, the average daily temperatures in both New Zealand and most of Australia are below 20⁰C.

Lower air temperatures can have a significant effect on the heat loss and energy savings of a SWH and, when

combined with the lower available solar energy in winter can result in SWHs being more reliant on electric or

gas boosting during the cooler months.

The Standard AS/NZS 1056.4 provides some useful insights into how temperature affects energy usage for a

conventional electric system, results which are very relevant to SWHs. Total energy used by a water heater

relates to two factors. First is total energy demanded by the user and the associated expansion losses from

heating this water. Expansions loss is the energy lost from the hot water that may trickle out of a water heater

while it is heating. The second factor is the in-use tank heat loss which is the standard tank heat loss result

adjusted depending on air temperature, the temperature of water in the tank and the temperature of water

demanded.

Expansion losses appeared to be ignored in modelling and claims and for a 75oC water heater these losses

increase energy usage by 2.1% to 2.6% depending in local water temperatures14.

The temperature factor will have the effects listed below when compared to the standard tank-only heat loss

test performed at 20oC (assumes a 75oC thermostat setting and outdoor storage tank):

• 25oC mean temperature (far north Australia) actual losses are 9% lower;

• 20oC mean temperature (band of Australia between Geraldton and Brisbane) actual losses are

correct;

• 15oC mean temperature (areas of southern Australia including Sydney and far north New Zealand)

actual losses are 9% higher; and

• 10oC (many alpine areas and much of New Zealand’s South Island) actual losses are 18% higher.

However the heat losses from a SWH are not just from a storage tank, but from the collector and associated

pipes. So to investigate the impact on SWHs three electric boosted systems were tested for system heat loss in

ambient air temperatures of 35oC, 20oC, 10oC and 2oC, with the storage tank water temperature kept constant

at 75oC. These temperature points were chosen to investigate how system heat loss levels varied with

temperatures both hotter and colder than the standard 20oC. A temperature of 2oC was chosen as a

temperature point close to but just above zero to avoid the possibility of the water freezing during testing and

the systems being damaged.

Figure 18: System heat loss at various air temperatures

14 AS/NZS 1056.4 Table 2.


The results of the system heat loss tests are shown in Figure 18. For all systems, total system heat loss per day

decreased as the air temperature increased. The difference between tank heat loss at 20°C and system heat

loss at 10°C was 43% for Model E1, 35% for Model E2 and 32% for Model E8. This is considerably larger than

predicted in in AS 1056 where the difference was expected to be approximately 9%. Another interesting

comparison was the difference in system and tank heat loss at 20°C where the differences observed were 21%

for Model E1, 15% for Model E2 and 12% for Model E8. The results obtained show that the systems lose much

more heat in real life than the standards anticipate.

The system heat loss results at 2°C show a large difference between how much heat each of the systems lose

in cold temperatures. Model E2 lost a much greater amount of heat than the other two as it uses the

circulation pump for frost protection. At 2°C, the frost protection system was triggered and the circulation

pump was switching on, resulting in warm water circulating through the collector and losing more heat than

in the storage tank. Model E2 lost 7.34kWh of heat at 2°C, which is a significant amount of energy,

considering that a two person Australian household in Melbourne uses an average 15kWh of energy per day

in winter, while an equivalent household in Hobart uses an average 31kWh of energy per day in winter.

The systems lost a much greater amount of heat at 2°C than in both the system and tank heat loss tests at

20°C. Model E2 lost 4.24kWh more heat than the 20°C tank test, which is an increase of 137%, and lost

3.76kWh more than the 20°C system test, which is an increase of 105%. Model E1 lost 1.46kWh more heat

than the 20°C tank test, which is an increase of 63%, and lost 0.97kWh more heat than the 20°C system test,

which is an increase of 34%. Model E8 lost 1.41kWh more heat than the 20°C tank test, which is an increase

of 39%, and lost 0.95kWh more heat than the 20°C system test, which is an increase of 23%. Model E8 uses a

heat transfer fluid containing a mixture of glycol and water, which acts as a form of frost protection and may

contribute to the slightly lower difference in system heat loss between 20°C and 2°C compared to the other

two systems.

For completeness in discussing the heat loss test requirements in AS/NZS4692.1, the Standard also states

that the air movement for these tests should be ‘0.25 m/s (0.9km/h) and 0.5 m/s (1.8km/h) at positions

adjacent to the container’. Wind is important as higher air flow leads to additional heat being lost from the

storage tank. To provide some context to the wind speed levels in the Standard, data from the Australian

Bureau of Meteorology (BoM) over a fifty four year period gives an average wind speed in Melbourne of

12.3km/h15. The BoM measurements are taken at a height of 10m above the ground surface. The wind

experienced by a thermosiphon will be less than this as it is closer to the ground and may have a degree of

wind shelter from a sloped roof or near-by trees or buildings, while an external, split system storage tank may

be further sheltered due to dwelling walls, fences or other structures.

If it was assumed that a SWH was sheltered from 66% of the wind, a rough calculation shows that the tank

would be expected to experience an average wind speed of 1.1m/s (4.1km/h) in Melbourne which is two to

four times the wind speed levels in the Standard. So again there appears to be an additional metric within the

Standard that is likely to lead to underestimated heat loss levels for many SWHs tanks. It is not possible at

this time to calculate the magnitude of the effect of using higher wind speed levels in testing. One

manufacturer has raised concerns about the accuracy of measuring the low wind speeds in the Standard.

There may be a case for either increasing the wind speed to provide more relevant results or to remove any

wind requirements, simplifying testing, but to impose a simple calculated adjustment to the heat loss result

recorded in the nil-wind conditions.

The result of the heat loss testing has shown that a number of sources of energy loss are being ignored in the

energy savings modelling and associated consumer information – expansion losses (2-2.6% error), ‘system’

losses from solar collectors and associated piping of 12% for a thermosiphon system and ranging from 15% to

21% for split systems and the 20°C tank test point being unrepresentative for many solar system (error varies

but is 9% for Sydney and will be higher in winter when more boosting is typically needed). Wind speed levels

may also be too low and further understate heat loss levels for SWH. So overall there is a clear

understatement of energy losses in information being provided to consumers to inform their purchases.

However, as some of the energy losses will be replaced via solar energy the actual real-life cost impact cannot

15 Measurements are taken at 9 am and 3 pm daily averaged over a period of 10 minutes leading up to the time of the reading.


be accurately noted at this time –rough estimates suggest costs for some users could be around $85 to $117

per annum higher for medium or large SWHs respectively16.

Collector test results

Collector efficiency

All eight collectors supplied with the electric boosted SWHs were tested for efficiency to AS/NZS 2535.1 – all

eight were tested against the indoor test method and three were tested against the outdoor test method. Both

indoor and outdoor tests were performed to investigate potential differences in collector efficiency between

the two test methods. For more detail on the outdoor collector test and how the results compare to the indoor

collector test, see Appendix 4.

In the indoor test, the efficiency of the solar collectors fell into three groups. The evacuated tubes were the

most efficient technology when there was a large temperature difference between the water in the collector

and the surrounding air, for example when heating high temperature water, followed by the flat plate

collectors, which in turn fell into two separate groups.

The difference between the efficiency of the two groups of flat plate collectors is related to the type of surface

coating on the collectors. The flat plate 1 group had selective coatings, while flat plate 2 group didn’t have a

selective coating.

However, it should also be noted that when there is a low temperature difference between the air and the

water (such as when hot water in a storage tank has been fully or largely used), the flat plate technologies

were more efficient at heating water. This has interesting implications as it appears that evacuated tubes are

the best technology for commercial type SWH that require water at very high temperatures, but for domestic

use the most efficient collector type is unclear and may depend on the tank to collector ratio e.g. a household

may choose a small tank that can be heated to a very high temperature with evacuated tubes or a larger tank

that heats more water but to a slightly lower temperature with a selectively coated flat plate. Of course if roof

area is not a concern it could be more cost-effective to install a larger area of the less efficient non-coated flat

plates.

Similar solar collector performance results have been observed in a report for the South African National

Energy Research Institute (SANERI) (as referenced in Dintchev, 2009).

As shown in Figure 19 below, the efficiency of a solar collector decreases as the temperature difference

between the air and water in the collector increases. This is to be expected, as heat loss from the collector will

be greater when the air temperature is lower than the water temperature. Figure 19 also shows that the

efficiency of evacuated tubes decreases at a lower rate than the efficiency of flat plates.

16 AS/NZS 4234 assumes a large electric system in zone 3 uses 21,000MJ (5,833Kwh) and a medium system 15,260MJ (4,238kWh). If,

after solar gain, the sum of the errors created 10% additional annual energy usage (583 and 424kWh p.a.) this would cost around $117 or

$85 per year based on $0.20 kWh electric tariff.


Figure 19: Instantaneous collector efficiency17

Collector impact resistance

The purpose of the impact resistance test was to evaluate the ability of the collector to withstand impact

forces from hailstones or similar projectiles.

The collectors were all tested using Method 1 of AS/NZS 2712. The test involves the collector being hit with a

small steel ball, which is considered to be a greater impact than what would generally be experienced in the

real world. It is generally used in impact testing as it is a cheaper and easier test method than a separate ‘ice

ball’ method (Method 2 in AS/NZS 2712). Collectors must be able to pass the ice-ball test but can choose to

pass the harder, cheaper steel ball test.

Of the eight collectors tested, all of the six flat plate collectors passed the steel ball test, while both of the

evacuated tube collectors failed. The two evacuated tube collectors were tested again using the ice ball test.

One of the evacuated tube collectors passed this test, and one failed. This means that one of the collectors on

the market did not meet the minimum resistance requirements but no bodies, government or industry,

appear to be conducting physical compliance to remove poor products from the market.

Resistance to freeze damage

The eight collectors from the electric boosted SWHs were tested under low ambient temperature and clear

sky conditions to determine their resistance to damage from freezing as per AS/NZS 2712. Clear sky

conditions at night are when maximum cooling occurs due to the lack of cloud cover to act as an insulating

layer. Resistance to freezing is very important in many areas of Australia and New Zealand to prevent

systems being damaged and breaking and all SWHs are required to state on the solar collector whether or not

they are frost protected and to what level they are protected.

The collectors were tested to AS/NZS 2712, which allows for freeze resistance testing of only one panel.

However, the E3 tests were performed with number of panels that were sold with each system to better

represent real world operating conditions and performance, as well as satisfying manufacturers’

recommendations for the collector area to be installed with a system. Using multiple panels in testing allows

the water/heat-transfer fluid more time to cool down in the collector and will provide a more realistic test of

each a system will fail in freezing conditions.

17 Collector efficiency is tested dependent on absorber area and the difference between mean water temperature in the collector and

ambient air temperature.


Thermosiphon systems were tested with the tank inside the test chamber, while split systems had the tank,

controller and pump located outside the chamber, as specified in the standard. Thermosiphons located on

the roof are exposed to weather conditions such as frost, wind and low temperatures and are susceptible to

higher levels of tank heat loss. Split systems on the other hand, are less exposed to these weather conditions

as the tanks are generally located indoors or against a house wall. Data from a 2012 BIS Shrapnel study

suggests that the majority of SWH split systems have the storage tank located outside.

Three of the eight systems tested were declared as frost protected and of these, one failed the freeze test. For

a full description of the freeze tests, including observations of how components performed and detailed

graphs of system performance, see Appendix 4. One from three collector systems failing is a concern as it

may mean that many consumers in areas susceptible to frost are purchasing systems that may fail in frost

conditions.

Model Declared frost protection Pass/Fail

Model E1 (SE250) Yes Pass

Model E2 (SF415)18 No Pass

Model E3 (SF270) No Fail

Model E4 (SF325) No Fail

Model E5 (SE340) Yes Pass

Model E6 (TF305) No Fail

Model E7 (TF330) No Fail

Model E8 (TF300) Yes Fail

Table 10: Summary of freeze test results

Full physical system tests and model checking

Performance in the field

As well as doing performance tests on SWH components as per Standards or system tests under a range of

extreme conditions, it was considered important to test SWH systems under conditions experienced in the

field. This testing would give an indication of how the systems would be expected to perform in everyday

domestic situations, without the strict controls of a test environment and will provide insights into how well

computer simulations are at actually predicting performance. The results of these physical tests were also

then used as inputs into the energy saving model to test how well the model is estimating actual energy

usage.

Three electric boosted SWHs were tested for real world performance with a mix of tank sizes and

technologies– Model E1 (SE250), Model E2 (SF415) and Model E8 (TF300). The systems were assembled

according to manufacturer’s instructions, with electric element thermostats set at 60oC and the tempering

valves set as close to 50oC as possible. There was also a conventional electric storage water heater (i.e. not a

SWH) tested as a reference point. While the tests weren’t standard tests, they were tested in general

accordance with AS 2984.

There were three scenarios covered in the field trials:

• Scenario 1 – No hot water draw-offs with element activated

• Scenario 2 – Hot water drawn-off over a 24 hour cycle with element activated

• Scenario 3 – Hot water drawn-off over a 24 hour cycle with element deactivated

Each scenario was run for a minimum of four weeks, with tank temperatures allowed to stabilise before

testing began. The hot water draw-offs were done according to the hot water loads specified in AS/NZS 4234

Appendix A. If any systems delivered water below 45oC then all hot water draw-offs for that system were

18 This system was fitted with a frost protection valve.


stopped for the remainder of the day to simulate a household choosing not to shower/bathe in colder

temperatures.

Due to differences in solar irradiance and air temperature between the testing of each scenario, test results

for each system within each scenario can be compared, but results can’t be directly compared between

scenarios.

Scenario 1: No load with element activated

Scenario 1 of the field performance testing was the no hot water load draw-off, where the system was set up

and operated consistent with previous standard component tests, but had no hot water taken from the tank.

This was to look at actual energy use of the systems based on system heat loss or pumping requirements and

replicates the conditions experienced by a water heater when not in use (e.g. the owners are on holidays).

Figure 20: Cumulative energy use for Scenario 1

As Figure 20 shows, Model E8, a thermosiphon systems, used no energy during the no hot water draw-off

test as it did not have a controller or circulation pump. Model E2 used very little energy, which was to run the

circulation pump and controller.

However, Model E1 used a relatively large amount of energy (average 0.52 kWh per day) considering that no

hot water was drawn off. A small amount of this energy was used to run the circulation pump and controller,

with the rest being used by the element, as shown in Figure 21. Over 30 days of testing, Model E1’s electric

element used energy on ten of those days, despite being exposed to sunlight and having no hot water drawn

off – a very poor result for a SWH. Figure 21 shows the underlying energy use and climatic conditions for

Model E1. These results are very informative as a SWH should not be using booster energy in such

conditions. Additionally the consumer would likely be unaware of the energy usage (and energy cost) of a

poorly performing system that is using its booster in these conditions.


Figure 21: Energy use for Model E1 (SE250) during the Scenario 1

The climatic conditions and other measurements from the Scenario 1 testing was inputted to the energy

savings model to see how well the model was able to replicate the actual measured energy usage levels from

the physical tests.

For the split systems there was a small but distinct difference between the results obtained from modelling

and physical tests for the electrical energy used. For Model E2, the difference averaged 0.08 kWh/day during

Scenario 1. This difference is partly due to the model not requiring the energy of the ‘controller’ for SWH to

be included in the calculations. For all the systems there was a difference in determined heat loss from the

tank (used by the model) compared with actual heat loss from the whole system.

A more substantial error occurred for Model E1. The frequency of the heating element activating was

underestimated as can be seen in Figure 22. The energy savings model does not ‘directly’ include instructions

on how often a heating element is used, but rather it estimates how often it will come on based around the

heating element ‘instructions’ of the SWH and assumptions about how the temperature of water in the

storage tank changes in response to water usage, solar gain and heat loss. This means the underestimated

heating element usage is a ‘symptom’ of an underlying aspect in the model not correctly anticipating how the

actual SWH behaves. It is likely that the fault is due to Model E1 not operating as intended, but this is a good

example of how the model can be a great tool, but it is not able to to identify underlying problems in a SWH.

The scale of the error in this case was 0.4kWh energy usage per day but the effect of the error may well be

more pronounced in winter (the testing was carried out in summer conditions where higher solar gain may

have been able to offset some of the problem).


Figure 22: Comparison of energy used for Model E1 (SE250) during Scenario 1

A table showing the actual energy usage and the modelled energy usage for each of the systems and for each

of the scenarios is in Appendix 4.

Scenario 2: Tapping load with element activated

Scenario 2 of the field performance testing was the hot water draw-off test with the boosting element

activated. The SWH was set up consistent with previous standard component tests, and hot water was taken

from the tank at intervals defined in AS/NZS 4234 Appendix A – this Standard contains the specified hot

water loads used when companies make energy savings claims. Eight draw-offs occurred during each 24 hour

period, with an equal amount of energy drawn off each time.

This test provided additional information on how the systems perform under real world conditions, including

the amount of hot water delivered in response to demand and the associated energy used. It is also a good

test to see how accurate the energy savings model is a predicting the actual energy use associated with the

defined hot water loads that industry use to make public claims.


Figure 23: Cumulative energy use for Scenario 2

Figure 23 shows that the cumulative energy use for Model E1 is almost the same as the energy use of the

reference conventional electric system – i.e. Model E1 offered very little energy savings at all. Model E2 and

Model E8 both offered reasonable energy savings compared to the reference electric system. It is unclear why

Model E1 used a much greater amount of energy than Models E2 and E8. Possible influencing factors include

differences in element location within the tank, collector type, controller parameters, thermostat location,

pump behaviour, tank size, etc. While the manufacturer of Model E1 could not be contacted for comment,

other manufacturers have suggested that a poorly designed control system could have been to blame. This

would mean that the circulation pump was operated to often and the result is that hot water can be pumped

out of the insulated storage tank, to the collector and pipes, where it was cooled rather than heated. When

energy savings claims are made by manufacturers, it will generally be assumed that components are working

so faulty or poor quality components or design work will lead to consumers being misled over actual possible

energy savings – an issue common to many types of products, not just SWH.

Additional details on Model E1’s energy usage and other scenario data, including how energy usage varied for

each week of the test in response to changing climate conditions, are at Appendix 4.

When the actual test conditions (temperature, solar irradiation etc.) were used as inputs for the ‘energy

savings’ model along with the results and observations of the physical testing, the energy savings model

appeared to underestimate energy usage to a small degree on average. Two of the solar systems and the

reference electric system used more energy during the physical tests that the model predicted – but the

model overestimated the energy usage for E2. For E1, the energy savings model underestimated energy usage

by around 20% but this appears to be due to a faulty controller which the model ‘assumed’ would operate

correctly. Some of the remaining small differences observed can be attributed to different loads being drawn

down during the physical tests, but there were also the errors relating to the absence of controller energy

requirements and differences between system and tank heat losses. The hot water loads and the mean energy

usage figures for both the physical tests and the associated modelled outcome are in Table 11.


System Mean daily delivered energy

(kWh)

Mean daily electrical energy

consumed (kWh)

Model Physical test Model Physical test

Model E1 (SE250) 10.50 10.50 10.05 12.53

Model E2 (SF415) 10.50 10.37 5.45 5.19

Model E8 (TF300) 10.50 11.11 6.02 6.92

Reference electric

system

10.50 10.92 12.15 13.90

Table 11: Comparison of energy from model and physical test during Scenario 2

During Scenario 2, the delivered load energy was higher than the modelled value. Given that the energy usage

figures were measured and modelled during summer and autumn, it is reasonable to expect that the

difference would be higher in winter when system heat loss and supplementary boosting requirements are

much higher. The results obtained from the modelling are very similar to those obtained during physical tests

whether the performance of the system was poor or not.

Figure 24: Comparison of energy used by reference electric system during Scenario 2

Figure 24 shows that the electrical energy used in the physical test was higher than that predicted by the

model. This means that the modelled energy savings for solar water heaters is being overestimated.

Scenario 3: Tapping load with element deactivated

Scenario 3 of the field performance testing in the field was a hot water draw-off test with the element

deactivated. The SWHs were set up consistent with as per the above scenarios but the electric elements were

deactivated and the system relied solely on solar energy to heat the water. With no boosting possible, the

impact of hot water usage stopping if temperature fell below 45°C had a large impact on the quantity of hot

water that could be delivered.


This test provided information on how the systems performed with the booster switched off, as some

consumers may choose to run their SWH with the booster switched off at times, to save on energy costs. It

also provides insights into how much hot water different SWHs are able to provide with ‘free’ solar energy

which is important for consumers who wish to reduce their energy usage as much as possible.

All three systems used almost no electrical energy during the test. Model E1 and Model E2 used a very small

amount of energy to operate the controller and circulation pump –a total cumulative energy use of

approximately 8 kWh and 6 kWh respectively. Model E8 is a thermosiphon, with no controller or circulation

pump, and therefore used no electrical energy during this test.

However the most important outcome from this test is how much hot water was able to be drawn-off for each

of the systems. With the element deactivated, the SWHs delivered a much smaller amount of hot water than

the reference conventional electric water heater19 which delivered the ‘full’ amount of hot water demanded

(Figure 25). Model E1 (system with the smallest tank (250L)) delivered the least amount of hot water and

Model E2 (system with the largest tank (415L)) delivering the most. A fairer comparison based on the

percentage of the SWH tank volume that was able to be delivered also had Model E1 with the poorest results

with Model E8 generally the superior systems. However, the amount of water delivered by each system for

each of the five weeks in the test period varied substantially with changing air temperature and solar

irradiation (Figure 26).

Figure 25: Cumulative water delivered for Scenario 3

19 The reference conventional electric water heater in the Scenario 3 test had its electric boosting element enabled (otherwise it would

have delivered no hot water). The data on the reference conventional electric water heater is provided for comparative purposes to

illustrate the maximum level of hot water demanded under the Scenario.


Figure 26: Average weekly irradiance and amount of hot water delivered, as a percentage of tank

volume, during Scenario 3

Gas solar water heater system testing

The gas boosted SWHs were all tested against the gas consumption MEPS requirements and thermal

efficiency, and other applicable energy efficiency related clauses in AS 4552. Four of the systems had

instantaneous gas boosters while two had in-tank boosters.

AS 4552 states that the determined (tested) gas consumption must be within 5% of the nominal (declared)

gas consumption. As shown in Table 12, four of the six gas boosted systems complied with the 5%

requirement while two failed to meet the Standard.

System Gas consumption (MJ/h) AS 4552

Compliant Nominal Determined Variation

Model G1 (TI180) 153 157.1 +2.7% Yes

Model G2 (TI305) 205 204.6 -0.2% Yes

Model G3 (SI165) 199 210.9 +6.0% No

Model G4 (SI215) 125 133.4 +6.7% No

Model G5 (SS322) 45 45.2 +0.5% Yes

Model G6 (TS300) 13 12.9 -0.7% Yes

Table 12: Comparison of nominal and determined gas consumption

There was little difference in thermal efficiency between the six gas boosted systems. The thermal efficiency

of a gas water heater is how well the conversion from gas energy to thermal energy is accomplished. Thermal

efficiencies ranged between 78.9% and 83.4%, as shown in Table 13. AS 4552 states that the thermal

efficiency of appliances operating at nominal gas consumption should not be less than 75%, so all of the

systems tested passed this requirement. It is interesting to note that the two gas storage systems recorded the

best and the worst result, so overall the instantaneous and storage system results appear broadly comparable.


System Thermal efficiency (%)

Model G1 (TI180) 80.2

Model G2 (TI305) 80.7

Model G3 (SI165) 79.5

Model G4 (SI215) 79.4

Model G5 (SS322) 83.4

Model G6 (TS300) 78.9

Table 13: Thermal efficiency of all gas boosted systems

Both storage systems (Models G5 and G6) had their maintenance gas consumption measured and compared

to the maximum limit. Maintenance gas rate is the gas required to keep the water inside the storage tank at

45oC above ambient air temperature. Both Model G5 and Model G6 had a determined maintenance rate

below the maintenance rate maximum limit, as specified in AS 4552.

All six gas boosted SWHs were found to comply with the gas MEPS requirements, which has a maximum

allowable annual energy consumption of 22,381 MJ/year.

In conducting the gas tests the two storage systems both had problems in being tested to the Standard and

required attention by the test laboratory. Model G5 had a thermostat that was fixed at 70oC rather than 60oC

and the thermostat was not adjustable (by either a consumer or an installer). As the Standard has test

requirements based heating to 60oC the results of Model G5 had to be adjusted. More problematic was

Model G6 which was unable to achieve the 60oC tank water temperature required for testing. Even when

Model G6’s thermostat was adjusted up to 70oC it was not able to suitably raise the average tank water

temperature20. The likely reason for the low average tank temperature was the close proximity of the

thermostat to the burner and a lack of water circulation in the system – a probable design flaw which would

impact the ability of the consumer to access a large amount of hot water outside periods of solar gain.

Performance testing of instantaneous gas systems

Current test methods for performance of instantaneous gas systems (including SWH gas boosters) as

outlined in AS 4552 require them to be tested with a 15oC inlet water temperature. For gas boosted SWHs,

this test doesn’t simulate actual operating conditions, as the inlet water temperature may already be

substantially heated due to solar gain.

Four tests performed on the four instantaneous gas boosted systems that aimed to assess the systems’

behaviour when operated with water at various inlet temperatures. These tests were not standard tests, but

were performed to simulate real world conditions for gas boosted SWHs.

The parameters that were monitored during testing were inlet and outlet water temperature, water flow rate,

average gas rate, delivered water volume and delivered gas volume. Gas instantaneous systems are able to

manage the outlet water flow rate so that the water can be provided time to heat to the desired temperature.

The tests were performed using the maximum water flow rates at which the systems could operate.

The four tests were:

• Test 1 – No solar preheating - 15oC inlet water temperature

• Test 2 – Warm water, some boosting needed - inlet water temperature 10oC below the default outlet

temperature setting

• Test 3 – Changing water temperatures - initial 15oC inlet water temperature, increasing to 10oC

below the default outlet temperature setting

• Test 4 – Hot water, marginal boosting needed - inlet water temperature 3oC below the default outlet

temperature setting

20When the thermostat was set to 70oC, the average tank water temperature only achieved 39.2oC above ambient, where the standards

require an average tank temperature of 45oC above ambient temperature. Ambient temperature during the test was 20°C


Water and gas flow rate

The results from this testing show that a colder water inlet temperature will result in a lower water flow rate,

as cold water requires more time to heat to the desired outlet temperature and therefore must pass more

slowly through the booster. The average gas consumption was also much higher than with high water inlet

temperatures, as a larger amount of energy was required to raise the temperature of the cold water.

There was one system, Model G2, that had a significantly higher water flow rate in Tests 2 and 4, despite its

required water outlet temperature being the same as, or lower than the other three systems. So this unit has a

higher ability to meet high water demand.

Test 3 involved a large change in inlet water temperature halfway through the test. Most systems responded

to the temperature change similarly and in an expected manner, with an increase in water flow rate and

decrease in average gas rate, due to only needing to boost the water temperature a small amount. The

systems generally responded to the inlet water temperature change quickly, however one model required

longer to stabilise the supplied water temperature.

Temperature stabilisation

It is desirable for instantaneous boosters to quickly stabilise at the required outlet temperature, as

temperature ‘overshoots’ can result in unnecessary gas consumption. The additional gas consumption

associated with overheating water is an issue when small amounts of hot water are being drawn off, as the

excess heat being produced is not used but wasted. It is less of an issue when large amounts of hot water are

used, as the original overheated water can be completely utilised. Any safety issues with overheated water are

managed by the tempering valve which regulates the outlet water temperature by mixing hot and cold water

as required.

With a cold water inlet temperature, Model G4 reached the stable desired temperature very quickly, but the

other three systems had some temperature fluctuations and took a little longer to stabilise. Model G3

overshot the desired temperature by approximately 6oC and took approximately two minutes to stabilise,

while Model G2 took just over two minutes to reach the required temperature and Model G1 fluctuated only

slightly, taking approximately a minute to stabilise.

In the high water inlet temperature tests (Tests 2 and 4), Models G1, G2 and G3 had very small overshoots in

water outlet temperature and then stabilised very quickly, generally within approximately 20 seconds.

Model G4, overshot the required water outlet temperature significantly and took much longer to reach a

stable temperature. In Test 2, Model G4 overshot the required temperature by 17oC and took approximately

90 seconds to stabilise. In Test 4, it overshot by 22oC and took approximately 90 seconds to stabilise.

Overshooting by 22oC when only 3oC of warming was required means that Model G4 is poorly suited to

situations where only some boosting is required – conditions that may occur often during the year.

TRNSYS modelling of test results

Sensitivity modelling for pipe insulation and pipe length

TRNSYS modelling to AS/NZS 4234 was conducted for all of the electric boosted SWHs to determine their

sensitivity to changes in insulation thickness and pipe length between the tank and collector. As these pipes

carry the solar heated water from the collectors to the tank, their length and level of insulation has an effect

on heat losses. Full results are at Appendix 4.

The results of the insulation thickness modelling show that the thickness of pipe insulation is a material

consideration especially in colder areas, for split systems and for systems that utilise evacuated tube

collectors. Additionally the results of the pipe length testing demonstrated the preference to locate a storage

tank as close to the collectors as feasible, but the importance of this for the evacuated tube systems was far

greater. In particular, the two evacuated tube collector systems modelled were much more affected by

changes in pipe lengths, with an average 9% decline in energy savings for Model E5 and an average 15%

decline for Model E1 when pipe lengths increased from 5m to 15m. This preference to locate storage tanks as

close as possible to solar collectors also needs to be weighted up against the preference to locate collectors on

the section of the roof receiving the most solar irradiation.


Impact of different methods of boosting on modelled energy savings

Two systems were modelled using four different boosting methods to examine how the level of energy

savings were affected by the boosting approach for each climate zone. The results are important for

informing what is the ‘best’ boosting option for a consumer.

The following boosting approaches were modelled:

• continuous electric boosting;

• manual boosting (assumes the consumer turns on the booster when the outlet water temperature

drops below 45oC);

• off-peak boosting (daily boosting between 10 pm and 7 am); and

• in-line (instantaneous) gas boosting.

The graphs in Figure 27 and Figure 28 show energy savings for each boosting method relative to the lowest

energy savings value (continuous electric boosting in zone 6 for both graphs).

The impact of boosting method on energy savings varied substantially between models. Model E2 showed a

very similar pattern of energy savings changes between climate zones for each of the boosting approaches

(Figure 27). Off-peak electric boosting gave the highest annual energy savings for Model E2, although there

wasn’t a large difference between all methods of boosting, with an average 11% difference between the

highest and lowest energy savings in each climate zone.

For Model E2, there was a noticeable change in which type of boosting provided the lowest energy savings. In

climate zones one and two, in-line gas boosting gave lowest energy savings however, in zones 4, 5 and 6, both

continuous electric and manual boosting gave the lowest energy savings.

Figure 27: Impact of boosting method on energy savings for Model E2

Model E1 was much more sensitive to changes in boosting method and climate zone (Figure 28). In-line gas

boosting gave the highest annual energy savings for Model E1 in all climates and especially in colder climate

zones. This is likely due to Model E1’s smaller storage tank, which means that under continuous electric

boosting, boosting would switch on any time the tank temperature fell too low which may occur often and

this decreases the ability for energy to be sources from solar input. The average difference between the

highest and lowest energy savings for each climate zone for Model E1 was 42%.


Figure 28: Impact of boosting method on energy savings for Model E1

Comparison of actual and modelled freeze test results

To test the accuracy of TRNSYS modelling at low temperatures, the collector freeze tests were replicated in

the TRNSYS model. The modelled results were then compared against actual observations of SWH

performance under freeze conditions. Full details are at Appendix 4.

The results of the comparisons identified some key shortcomings of the TRNSYS modelling that may have

large implications for the accuracy of the model in cold conditions.

The first shortcoming relates to the amount of energy lost by split systems (regardless of collector types or

usage of indirect heat transfer substances).

The freeze tests involved six freezing cycles as set out in the joint Australian and New Zealand Standard,

AS/NZS 2712. Under normal operating conditions, the circulation pumps turn on to circulate warm water

into the collectors to keep the water temperature inside the collector above 0oC and prevent freezing of the

system. This affects the heat loss of the system and hot water availability to the consumer, as circulating

warm water from the tank to the collectors and cold water from the collectors to the tank will decrease the

average tank temperature and likely result in higher heat loss from the collector.

The standard for calculation of energy consumption of heated water systems, AS/NZS 4234 only takes into

consideration some types of frost protection that exist for a system. Although only Model E5 claimed frost

resistance, both Model E4 and Model E5 had a frost protection device in the form of a circulation pump that

switched on when water in the collector was 4oC or below and remained circulating water until the

temperature in the collector was 6oC (Model E4)/5oC (Model E5) or higher.

The second shortcoming relates to the TRNSYS model assuming that water is always liquid, regardless of the

ambient temperature. Some of the modelling scenarios had the temperature of the water in the collector go

below 0oC several times. In real life conditions this would result in water that is constantly freezing and

thawing in the collector. The change in volume due to water freezing and thawing will put the collector and

pipes under stress and it is likely that they will break. Such a breakage occurred in the actual testing of Model

E4 (SF325).

Table 14 shows the modelled heat loss for both individual components and the whole system in the freeze test

modelling. When these modelled heat loss results are compared to the actual measured system heat loss

during freeze testing, it can be seen that the modelled results understate the level of heat losses by 2.16kWh

or 4 %.


System Modelled heat loss (kWh) System heat loss (kWh)

Total of components Measured

Model E4

(SF325)

1.47 3.63

Model E5

(SE340)

1.75 2.23

Table 14: Difference between modelled and measured heat loss during freeze testing

Modelled and claimed annual energy savings- electric boosted SWHs

Most SWHs sold in Australia are registered with the CER as eligible for receiving STCs. The number of STCs

that each system receives is calculated based on the amount of electrical energy it saves in comparison with a

reference ESWH. These energy savings are calculated by modelling multiple inputs to AS/NZS 4234,

including climate zone, tank heat loss, hot water demand (load) and collector efficiency.

The results obtained from actual testing were used as inputs to model the annual energy savings and STC

entitlements in six climate zones, for the six electric boosted SWHs with flat plate collectors and all six gas

boosted SWHs. For inputs that couldn’t be obtained from test results, these came from either the installation

manual or were physically measured.

The STC entitlement was calculated according to the CER’s ‘STC Calculation Methodology for Solar Water

Heaters with a volumetric capacity up to and including 700 litres and Air Source Heat Pump Water Heaters

with a volumetric capacity up to and including 425 litres Version 2, March 2012’. This calculated entitlement

was compared to those that are claimed for each model on the CER website21.

Figure 29 shows that there is a general trend in all of the electric boosted SWHs for energy savings to be

greatest in zones 1 and 2 and lowest in zones 4 and 6. This is expected as solar irradiance is generally highest

in zones 1 and 2 and lowest in zones 4 and 6.

All of the flat plate systems had either equal to or greater than 60% energy savings in zone 3, which is the

benchmark the CER uses to essentially determine acceptable efficiency in Australia. If a system isn’t able to

deliver 60% energy savings in zone 3, it must be categorised as a smaller load system. All systems in this

analysis were modelled as medium loads for consistent and comparable data.

It should be noted that our testing assessed the systems against a ‘medium load’ while the load used by each

system for STC claims could differ. However as the load size used for an STC claim is not declared, modelling

each systems consistently as a medium systems is seen as useful for comparative purposes. Also, small

differences can be observed due to slight differences in test method, as the methodology for determining

many of the inputs, can allow for some flexibility in how the system is set up and tested. This must be taken

into account when evaluating the difference between results presented and claims made by manufacturers.

New Zealand models energy savings using different load sizes to the loads used when modelling energy

savings in Australia, which also impacts the ability to use the modelled energy savings shown in Figure 29 as

indicative of energy savings in New Zealand.

Model E1 and Model E5 failed to achieve 60% energy saving in zone 3 when modelled as a medium load.

Interestingly, Model E1 components performed well in the physical tests, yet the whole system performed

poorly. Sources have revealed that the controller in this system was faulty.

21 More information is available from: http://ret.cleanenergyregulator.gov.au/Hot-Water-Systems/eligible-swhs

http://ret.cleanenergyregulator.gov.au/Hot-Water-Systems/eligible-swhs


Figure 29: Modelled annual energy savings for electric boosted SWHs

Figure 30 shows the comparison of the modelled STC entitlements for the electric boosted SWHs and the

actual STCs that these systems receive in each climate zone. Again it should be noted that our testing

assessed the systems against a ‘medium load’ while the load used by each system for STC claims could differ.

However as the load size used for an STC claim is not declared, modelling each systems consistently as a

medium systems is seen as useful for comparative purposes.

Three of the systems have very similar modelled and actual STC requirements and for these systems, the

differences may be due to slight differences in test method. The methodology for determining many of the

inputs, can allow for some flexibility in how the system is set up and tested.

For the other three electric boosted systems, there are substantial differences between the modelled and

actual STC entitlements. These systems had an average difference between the modelled and actual STC

entitlements of 9 STCs but the differences are likely due to a different load size being modelled. If an average

STC price of $35 is assumed, a 9 STC difference would represent a $315 difference between the actual and

modelled entitlements.

If we assume that for the tanks with large differences, the gap is caused by the assumed hot water load size,

then it appears that claims, using the TRNSYS model reasonable but generally slightly overstated.


Figure 30: Comparison of current and modelled STC entitlements for electric boosted systems22

As mentioned earlier, there are many inputs used to determine the energy savings and STC entitlements of

SWHs and one of these inputs is heat loss. The current methodology uses tank heat loss as the heat loss input

however, a SWH loses heat from all of its components, including pipes and the collector. As shown in the

system heat loss test results, using tank heat loss isn’t fully representative of SWH heat loss and

underestimates the heat loss from the whole system.

These differences between tank and system heat loss can have an effect on STC entitlement. Figure 31 shows

that using system heat loss to calculate STC entitlement generally decreases the STC entitlement of a system

by a small amount in comparison to using tank heat loss.

Figure 31: Comparison of modelled STC entitlements using tank and system heat loss23

22 Note that there are no actual STC entitlements for zones 5 or 6, as zone 5 is a heat pump zone, and considered part of zone 4 for

SWHs, while zone 6 occurs only in New Zealand. Model E1 doesn’t have a current STC entitlement for zone 4. 23 Note that for Model E8 zones 3 and 5, the STC entitlement was the same for both modelled results, which is why there is no red band

visible.


Modelled annual energy savings and STC entitlements of gas boosted SWHs

The annual energy savings for each of the six gas boosted SWHs were calculated using TRNSYS modelling.

These energy savings were determined using the same method as for the electric boosted systems, with gas

energy also included.

Figure 32 shows that energy savings in zones 1 and 2 are much higher than in the other zones, which is to be

expected, as ambient air temperatures and solar irradiance are generally highest in zones 1 and 2.

In comparison to the modelled energy savings of electric boosted systems, the gas boosted systems generally

have lower modelled energy savings in zone 1 and higher energy savings in zones 3, 4 and 6. They also have a

lower variability in energy savings between climate zones when compared to the electric boosted systems.

All gas boosted systems were above the 60% energy savings in zone 3 benchmark that the CER uses to

determine acceptable efficiency for a defined load. Most of the systems were modelled as medium loads,

while Model G4 was modelled as a large load.

Figure 32: Modelled annual energy savings for gas boosted SWHs

Figure 33 below shows the comparison of the modelled STC entitlements for the gas boosted SWHs and the

actual STCs that these systems receive in each climate zone. These systems have very different results to the

STC entitlement modelling for the electric boosted systems. For all electric boosted systems, the actual

entitlement was higher than the modelled entitlement. However, for the gas boosted systems, there are

several models where the modelled STC entitlement is higher than the actual entitlement that systems are

eligible for.

It should be noted that all the systems with the exception of G3 were modelled with the collectors that were

recommended for the system. Three of the systems have very similar modelled and actual STC entitlements

and for these systems, the differences may be due to slight differences in test method, as the methodology for

determining many of the inputs, as well as energy savings, can allow for some flexibility in how the system is

set up and tested.

For the three other gas boosted systems, there are substantial differences between the modelled and actual

STC entitlements. Model G3 has an average difference of 12 STCs, but in this case, the modelled STCs are

higher than the actual STCs. For the other two models, the actual STC entitlement is higher than the

modelled STC entitlement. Model G2 has an average difference of 8 STCs, however Model G5 has an average

difference of 25 STCs, which could represent an $875 difference between actual and modelled STCs if an


average STC price of $35 is assumed. This large difference in STCs is most likely due to a difference in the

load size being modelled.

Figure 33: Comparison of current and modelled STC entitlements for gas boosted systems


The main advantage of SWHs over other types of water heaters is that they can provide hot water with low

amounts of purchased energy, and as a result, have low running costs and greenhouse gas emissions.

Without this advantage, it is unlikely that consumers would consider SWHs, mainly due to their high cost.

There appear to be many market failures causing barriers to SWH uptake that exist in the Australian and

New Zealand water heater markets. These barriers affect the decisions consumers make when choosing a

water heater. The present pattern of sub-optimal water heater choice can result in significantly higher

economic costs to the consumer and community and higher greenhouse gas emissions than if consumers and

business could select the system optimal for their needs.

Market failures in the water heater market include a lack of information and split incentives, in which there

is conflict between the interests of householders and those who purchase the household’s water heater

(NSEE, 2010). For new dwellings, these market failures have generally been partially addressed by a range of

Australian building regulations, which encourage energy efficient water heaters to be installed.

However, the problem remains for replacement sales, which make up approximately 70% of the water heater

market. Replacement sales are generally quick purchases, where a failure of the existing water heater can

place the consumer in a stressful, time-critical purchasing situation. The high value that consumers place on

the continuing availability of hot water limits the time taken for research, selection and installation.

Approximately a quarter of purchasing decisions are conducted with no research by consumers. When

research is conducted, it is usually through third party plumbers (48% of purchases), brochures (22%) or

from a manufacturer (21%), which are all sources with a commercial interest (BIS Shrapnel, 2012). In these

circumstances, government intervention in the market may have the potential to improve the overall welfare

of the community if the intervention is aimed at correcting or reducing the impact of market failure.

In recent E3 water heater reports and associated consultation, the existence of such market failure have been

confirmed by most stakeholders including manufacturers, installers, and those representing consumers.

Market failures

Split incentives

The issue of split incentives occurs where the end-user of the water heater is not directly involved in the

purchase of the water heater but is likely to pay the ongoing energy costs. This occurs in both the rental

market (residential and commercial) and parts of the new home market.

Split incentives that apply in the water heater market include:

• Plumber/owner split incentive: Many water heaters are supplied by plumbers or purchased

based on advice provided by a plumber. Plumbers have an incentive to recommend and sell the water

heaters that provide the greatest profit margin while requiring the least effort to install –although

not all plumbers will act on such an incentive. Additionally, some plumbers may have a bias in the

brands they recommend due to their commercial links (e.g. free or low cost training programs, or

discount purchasing) with particular suppliers and manufacturers. In these situations, the owner’s

interest to obtain an efficient and suitable water heater may not be met. This separation of the owner

from the purchase of the water heater will be the case for many residential purchases.

• Landlord/tenant split incentive: A landlord has little incentive to purchase an efficient water

heater, and is likely to be motivated to minimise their capital outlay, as the landlord will not be liable

for the ongoing energy costs. The short-term tenure of many rental properties also reduces the

tenant’s consideration of energy costs (including water heating energy costs). The impact of this

incentive was highlighted by the ACOSS submission to the Australian Senate Committee’s ‘Reducing

7. Market failures, barriers and energy

efficiency


energy bills and improving efficiency’ report – it argued that this problem has resulted in ‘some of

the most vulnerable households living in the most inefficient properties in Australia’.

• Builder/owner split incentive: As the water heater is a relatively minor part of a building or

renovation project, and may be selected before the buyer is known, the motivation and opportunity

for the final occupant to influence the water heater selection will usually be limited. Typically, the

builder will be motivated to keep the purchase and installation costs low and will have no stake in the

long-term energy consumption costs the owner or user will bear. Considering that new builds

constitute a large proportion of SWH sales, there is potential for this split incentive to influence the

consumer choice process.

The nature of the water heater market and influence of split incentives suggest that many buyers of SWHs

will purchase the cheapest water heater available, with limited consideration of the ongoing operating costs.

This split incentives market failure applies to both the Australian and New Zealand markets and creates a

barrier to more efficient water heaters being installed.

Information failures

A key market failure in terms of SWHs is the significant information shortcomings that appear to exist in the

water heater market. There is an inability to easily compare products due to a lack of consistent and/or

reliable information and uncertainty surrounding ongoing energy costs

The SA Department of Manufacturing, Innovation, Trade, Resources and Energy considers the lack of

adequate, accessible information available to consumers about purchasing an efficient water heater to be the

primary market failure for why householders generally don’t consider lifetime costs of a water heater. These

issues often result in a purchase decision being made with limited knowledge or consideration of ongoing

energy costs, energy efficiency and system performance.

To make an informed decision, a purchaser of a water heater needs to consider two costs: the capital cost of

buying and installing the water heater and the ongoing energy costs to operate it. The capital cost is the

purchase price and installation cost, which is incurred up front and can be easily understood by a purchaser.

However, the operating cost, which largely relates to energy use, is incurred progressively and is more

difficult to understand and predict, although it can form a major component of the overall cost. A decision

made without appropriate knowledge or consideration of the operating cost is unlikely to factor in energy

efficiency.

Consumers may not be able to determine the ongoing energy used by an appliance without significant

research or outside assistance. This may allow opportunism, as a supplier could mislead a buyer on the

efficiency of a product, which the buyer is unable to verify. This risk of false or misleading information can

result in consumers focusing too heavily on purchasing costs. Even where consumers have access to

information, the complexity around the uncertainty of future use and energy costs may result in poorly

informed and sub-optimal decisions.

In Australia, the only public information reported in a consistent format is the number of small-scale

technology certificates (STCs) that each SWH model is eligible to create under the Commonwealth Small-

scale Renewable Energy Scheme. However, as STCs only provide an indication of renewable energy

contribution, not energy efficiency, they are not suitable for comparing the energy efficiency of SWHs.

Other ways in which performance claims are made are:

• As ‘percent saving on water heating costs’ usually in relation to a conventional electric water heater.

It is often not explained that this may correspond to a user’s actual existing water heater, and is

dependent on how the consumer uses hot water and the type of tariff they’re on.

• Some manufacturers claim that their SWHs are able to provide a reliable, constant supply of hot

water at all times of the day.

• Suitable down to certain temperatures for frost protected systems.

The type and amount of information provided to consumers varies greatly between manufacturers. While

most make claims on some aspects of performance, it is rare that much detailed information is provided, or

that there is any consistency between manufacturer information.


As a consequence of the lack of complete, consistent and reliable information on SWH performance, and the

variance in product performance:

• Consumers cannot be assured of getting a product that performs adequately;

• Consumers are unable to reliably identify SWHs with good performance and avoid poor performing

SWHs; and

• There is limited market pressure on suppliers to improve product performance.

It is important that both consumers and installers are able to trust and understand the information provided

to them about SWHs. This information must be clear, correct and address the system’s reliability and

performance (ESTIF, 2012). Without consistent and accurate information, consumers in Australia and

New Zealand are not able to compare key performance characteristics and energy efficiency of SWHs.

Other market barriers

Capital cost

The high upfront cost of SWHs is a barrier to SWH uptake by households in both Australia and New Zealand,

especially households with financial constraints or where a split incentive exists (Wasi & Carson, 2011;

Murphy & Donoghue, 2009; CEC, 2011; ESTIF, 2012b).

This is supported by the findings of the 2012 BIS Shrapnel survey, which shows that for those respondents

who considered alternative water heaters but eventually chose an ESWH, 67% said that capital cost was the

main reason they chose not to purchase a SWH.

Capital cost presents an especially significant barrier to low-income households, as highlighted in a 2013

ACOSS report. The report discusses that, despite the energy efficiency of household appliances having

increased, low-income households are likely to still have inefficient appliances, as they are not able to afford

the capital cost of new, more efficient appliances.

Perceived efficiency of solar water heaters

SWHs are presented to the market as low running cost, low emission water heaters that operate much more

efficiently than conventional water heaters. The message this implies to consumers is that there will be

minimal energy costs for water heating (Miller & Buys, 2010). This creates consumer expectations of high

efficiency, as well as high economic and environmental benefits. However, the extent of these benefits

depends on many variables, including the system chosen being suitable for the consumer’s needs, correct

operation by the consumer, the quality of installation and the quality of the SWH – if there is a problem with

any of these variables, the consumers high expectation may not be met and this can lead to negative feedback

regardless of the source of the problem.

Consumers may also have little access to information about how to maintain or optimally operate their SWHs

after installation. A study by the Institute for Sustainable Futures found that there were many SWH owners

who were not provided with an instruction manual or information about boosting. Some owners had no

knowledge of the need for system maintenance or the fact that they were able to choose how best to operate

the booster. While not directly impacting the purchase of SWH, if a consumer is not achieving the amount of

energy savings that they were led to expect or regularly run out of hot water, they may provide negative

feedback to other potential consumers and prevent additional SWH sales.

The lack of information also has an impact on the ability of installers to adequately install SWHs. The

installation of a SWH is much more complex than the installation of a conventional water heater, as there are

more components to be installed and connected. A SWH that has been incorrectly installed may cause

problems for the consumer that are costly to fix or affect the performance of their SWH. Installers may not be

fully aware of, or understand, the complexities of how a SWH is installed and operated. There are many

organisations that offer specific SWH training for installers. Attendance at such training may significantly

assist in improving the quality of SWH installations and resulting system performance.


Solar water heater performance issues

The risk of purchasing a solar water heater that does not perform well could undermine consumer confidence

in the SWH market.

Studies by BIS Shrapnel and ESTIF show that a significant proportion of consumers speak to family and

friends when deciding what type of water heater to purchase. The experiences consumers have with SWHs

will therefore have an effect on the decision-making around what type of water heater to purchase.

A review of online forums and consumer reviews suggests that many consumers have found that the SWH

they purchased did not meet their needs. The main forums for SWH discussion are Product Review,

Alternative Technology Association and Whirlpool24.

Common consumer complaints on online forums include:

• Water not hot enough;

• Poor installation and/or customer service;

• Boosting too expensive;

• Incorrect system size;

• Misinformed/unrealistic expectations;

• Leaking tank/collector/pressure and temperature valve;

• Constant collector discharge;

• Failed parts (pump, temperature sensor, pressure valve); and

• No/not enough insulation on pipes.

There are many examples of consumers on forums discussing their bad experiences with SWHs and that

these have caused them to go back to other, conventional types of water heaters. Many consumers who have

had a bad experience have stated that they will not try SWHs again and will pass this information onto

friends and family. The negative impact of dissatisfied consumers and the negative feedback they provide to

others is a long-lasting barrier, which can be extremely difficult to overcome (ESTIF, 2012c).

The findings above reflect the results of a 2010 report by Miller and Buys, which studies SWH installations in

a Queensland village. The report showed that many faults with SWHs do occur with many falling into the

categories of either installation errors or commissioning and certification failures. These faults, combined

with other possible faults, resulted in solar input ranging from 0% to 100% in the houses surveyed. Examples

of faults include tempering valves either not installed or incorrectly located (safety issue), incorrect location

of inlet and outlet connections (affects solar gain and amount of hot water that can be supplied), solar

collector not connected (zero solar gain) temperature sensors not installed (collectors will not correctly

operate) , solar controllers (computer) not installed (collectors will not correctly operate), incorrectly sized

gas pipe to booster (booster will not correctly operate), uninsulated pipes or pipes that had their insulation

melt (decreases system performance via heat loss), and final commissioning checks were not performed by

some plumbers/contractors (problems will not be identified and fixed). Studies like this show that there can

be good reason for consumers to have a lack of confidence in SWH performance.

There are a number of requirements to help prevent many of the above problems from occurring. The

Building Code of Australia (BCA) and the New Zealand Building Code have regulations on the installation of

SWHs in homes. These regulations cover aspects of installation such as insulation, temperature restriction

and valves required. There is evidence that these regulations are not always complied with by SWH installers.

In South Australia, the rate of Certificate of Compliance returns is possibly as low as 20% of installations,

which is considered unacceptably low (DMITRE, 2012).

In relation to the actual SWH systems, there are no regulations that require the energy efficiency of SWH’s to

be tested to a common standard, to carry labels indicating their energy efficiency or to meet any minimum

prescribed levels of overall energy efficiency or performance. The only energy efficiency regulation that

applies to SWHs (gas boosted) is the annual gas consumption MEPS, as outlined in AS/NZS 4552.2.

24 Product Review: www.productreview.com.au; Alternative Technology Association: www.ata.org.au and

Whirlpool: www.forums.whirlpool.net.au

http://www.productreview.com.au/

http://www.ata.org.au/

http://www.forums.whirlpool.net.au/


Most SWH suppliers in Australia choose to register their models with the CER to be eligible to create STCs

under the Renewable Energy (Electricity) Act 2000 (this is not a mandatory requirement). This process

estimates renewable energy contribution rather than direct energy efficiency, and does not use the product

assessment process and compliance framework including physical testing applied under the E3 energy

labelling and MEPS. The CER checks that all SWH models submitting registration for STCs meet the

AS/NZS 2712 requirements. It also performs audits on selected SWH models to ensure that their STCs have

been correctly calculated. This audit process involves investigating test reports and TRNSYS modelling files.

This can provide some level of assurance, but the TRNSYS model approach has a number of shortcomings as

discussed in the test results. The model assumes all the components in the SWH work as intended, and

appears to ignore or not fully account for some sources of energy loss and the model assumes that a SWH is

correctly installed.

So while there are a number of regulatory safeguards, a low level of compliance and checking and a limited

scope of regulations mean that many SWHs appear to be underperforming and that this underperformance

can cause damage to the reputation of SWHs more broadly due to negative consumer sentiment. However, it

is also important to note that any regulation or associated compliance checking does come at a cost.


SWHs are a very important technology as they provide improvements in energy productivity, lower running

costs and lower emissions levels than conventional water heaters. SWHs have also received strong support

from manufacturers via innovation, by consumers through direct investment and by governments through

range of rebates, grants, information programs and regulatory support in Australian building codes.

A number of issues related to SWH performance and energy efficiency have been identified in this product

profile. In light of these issues it is worth considering if any changes to the SWH market could deliver better

outcomes. The key issues raised in this product profile include:

1. Claimed ‘energy savings’ are slightly higher than independent test results using the defined industry

endorsed method.

2. Inability of consumers to select an appropriate water heater due to lack of accurate comparative

information

3. Potentially poor SWH performance in cold climates (not captured in Standards)

4. Weak compliance with component-based and installation requirements

The identified possible options that could be used to fall into four key categories:

1. No action

2. Improving standards

o Improving the current energy savings modelling

o Cold climate specific issues

3. Information measures

o Mandatory climate-based energy efficiency labelling

o Public information campaigns and registers

4. Quality/minimum assurance measures

o Government compliance checking

o Other compliance checking

o Government backed minimum energy efficiency standards

Some of the above broad options are mutually exclusive, so if one was advocated, other actions may be

unnecessary. Other actions are complementary as they would address separate underlying issues.

Undertaking any action to address these issues will typically carry both benefits and costs, so it is important

to understand the magnitude and distribution of any impacts when evaluating possible changes. Indeed it

should also be noted that the option of ‘no action’ also includes a number of costs as consumers may continue

to be provided with poor systems and reputational damage to the SWH industry.

Appendix 6 provides detailed discussion on how the above categories of actions could be implemented and

the degree to which the options might address the underlying problems/ opportunities. This Appendix is

provided to assist stakeholders to consider both the merits of an option and the issues relating to how

implementation could occur and who should undertake the implementation. The Appendix provides details

on options and possible responses to draw out the issues and seek more detailed responses from

stakeholders. It does not necessarily indicate E3 support for any particular approach.

Feedback from all types of stakeholders is critical to help to determine if the issues or opportunities identified

in this document actually exist, and if they do, what actions may help and what are the costs of such options.

Stakeholders are asked to comment on the questions presented on page 7 but any other related comments or

suggestions are also welcome.

8. Summary and discussion


Australian Energy Market Commission (AEMC), 2013, Electricity Price Trends Final Report: Possible future

retail electricity price movements: 1 July 2012 to 30 June 2015, AEMC

Australian Energy Regulator (AER), 2012, State of the Energy Market 2012, Australian Energy Regulator,

Commonwealth of Australia, Melbourne

BIS Shrapnel, 2012, The Household Appliances Market in Australia 2012 – Volume 4: Hot Water Systems,

BIS Shrapnel, Australia

Building Code of Australia (BCA), 2010, Building Code of Australia 2010, Australian Building Codes Board

Carrington, G., 2011, Comparison of solar and heat pump water heaters in New Zealand, report prepared

for the Parliamentary Commissioner for the Environment, 30 June 2011

CLASP and Navigant Consulting, 2011, Opportunities for Success and CO2 Savings from Appliance Energy

Efficiency Harmonisation, CLASP

Clean Energy Council, 2011, Solar Hot Water & Heat Pump Study, Prepared by Mito Energy for the Clean

Energy Council, January 2011

Commonwealth of Australia, 2012, Product Profile: Heat Pump Water Heaters, Commonwealth of Australia,

June 2012

Council of Australian Governments (COAG), 2010, National Strategy on Energy Efficiency, Commonwealth

of Australia, July 2010

Department of Climate Change and Energy Efficiency (DCCEE), 2010, Your Home Technical Manual, 4th

ed., Commonwealth of Australia, Canberra

Department of Resources, Energy and Tourism (DRET), 2013, Draft Consultation Regulation Impact

Statement: Heat Pump Water Heaters, Commonwealth of Australia, Canberra

Department of Environment, Water, Heritage and the Arts (DEWHA), 2008, Energy Use in the Australian

Residential Sector 1986-2020, Commonwealth of Australia, Canberra

Department of Finance, 2013, Gas tariff caps, Government of Western Australia, viewed 26/8/13 at

http://www.finance.wa.gov.au/cms/content.aspx?id=14706

Department for Manufacturing, Innovation, Trade, Resources and Energy (DMITRE), 2012, Review of the

South Australian Residential Water Heater Requirements: Option Paper, Government of South Australia,

Adelaide

Department of Planning, Single Dwelling Outcomes 05-08: BASIX Building Sustainability Index Ongoing

Monitoring Program, NSW Government

Energy Consult, 2012, Product Profile: Electric Storage Water Heaters, prepared for the Department of

Climate Change and Energy Efficiency, Commonwealth of Australia, Canberra

Essential Services Commission (ESC), 2012, Energy Retailers Comparative Performance Report – Pricing

2011-12, September 2012

European Solar Thermal Industry Federation, 2012a, Guide on Standardisation and Quality Assurance for

Solar Thermal, part of the “Global Solar Water Heating Market Transformation and Strengthening

Initiative”

European Solar Thermal Industry Federation, 2012b, Guidelines for policy and framework conditions, part

of the “Global Solar Water Heating Market Transformation and Strengthening Initiative”

9. Resources

http://www.finance.wa.gov.au/cms/content.aspx?id=14706


European Solar Thermal Industry Federation, 2012c, Guide for awareness-raising campaigns, part of the

“Global Solar Water Heating Market Transformation and Strengthening Initiative”

Garnaut, R., 2008, The Garnaut Climate Change Review: Final Report, Commonwealth of Australia 2008

George Wilkenfeld and Associates (GWA), 2004, NFEE – Energy efficiency improvement potential case

studies, residential water heating, prepared for Sustainable Energy Authority Victoria, George Wilkenfeld

and Associates Pty Ltd, Sydney

George Wilkenfeld and Associates, 2007, Specifying the Performance of Water Heaters for New Houses in

the Building Code of Australia, prepared for the Australian Building Codes Board, George Wilkenfeld and

Associates with Energy Efficiency Strategies and Thermal Design, December 2007

George Wilkenfeld and Associates, 2009, Consultation Regulation Impact Statement: Phasing Out

Greenhouse-Intensive Water Heaters in Australian Homes, prepared for National Framework for Energy

Efficiency, George Wilkenfeld and Associates with National Institute of Economic and Industry Research,

Syneca Consulting, Sydney

Grattan Institute, 2013, Getting gas right: Australia’s energy challenge, Grattan Institute Report No. 2013-

6, June 2013, by Tony Wood, Lucy Carter and Daniel Mullerworth, Grattan Institute

Green Energy Markets (GEM), 2012, Impact of market based measures on NEM power consumption, report

for the REC Agents Association and The Energy Efficiency Certificate Creators group, June 2012, Green

Energy Markets, Hawthorn

Green Energy Markets (GEM), 2013, Small-scale technology certificates data modelling for 2013 to 2015,

Green Energy Markets, Hawthorn

Independent Pricing and Regulatory Tribunal (IPART), 2013, Review of regulated retail prices and charges

for gas: From 1 July 2013 to 30 June 2016, IPART NSW, June 2013

Miller, W. and Buys, L., 2010, Gas boosted solar water heaters: Queensland case studies of installation

practices in new homes, in Solar2010, the 48th AuSES Annual Conference, 1-3 December 2010, Australian

National University, Canberra

Ministry of Business, Innovation and Employment, 2013, NZ Energy Quarterly, Wellington, New Zealand,

June Quarter 2013

Ministry of Economic Development, 2012, New Zealand Energy Data File, Wellington, New Zealand

Murphy, A. and Donoghue, M., 2009, The Adoption of Solar Water Heating: exploring the New Zealand

case, in 2009 Australian & New Zealand Marketing Academy Annual Conference, 27 November – 2

December 2009, Melbourne, Australia

Parliamentary Commissioner for the Environment (PCE), 2012, Evaluating solar water heating: sun,

renewable energy and climate change, New Zealand Parliament, July 2012

Saman, W., 2013, Practical Building Solutions for a Changing Climate: Solar options for homes and small

businesses in cool temperate climates, in 2013 Tasmanian Solar Conference, Friday 5th July 2013, University

of Tasmania, Hobart, Australia

Select Committee on Electricity Prices, 2012, Reducing energy bills and improving efficiency,

Commonwealth of Australia, November 2012

Wasi, N. and Carson, R., 2011, The Influence of Rebate Programs on the Demand for Water Heaters: The

Case of New South Wales, in Australian Agricultural and Resource Economics Society 2011 Conference

(55th), February 8-11 2011, Melbourne, Australia

Winton, 2008, Household Purchasing Behaviour Regarding Domestic Hot Water Systems, prepared by

Winton Sustainable Research Strategies for the Department of the Environment, Water, Heritage and the

Arts

http://ideas.repec.org/s/ags/aare11.html

http://ideas.repec.org/s/ags/aare11.html


Joint Australia/New Zealand standards

AS/NZS 1056.4:1997 Storage water heaters - daily energy consumption calculations for

electric types

Sets out a method for calculating the energy consumption of electric storage water heaters fitted with electric

resistance elements. Exemptions within this standard result in the standard not applying to gas water

heaters, solar water heaters, heat exchangers or heat pumps.

AS/NZS 2535.1:2007 (ISO 9806-1:1994) Test methods for solar collectors – Part 1: Thermal

performance of glazed liquid heating collectors including pressure drop

Establishes the methods for determining the thermal performance of glazed liquid solar collectors. It

contains methods for conducting tests both outdoors and indoors.

AS/NZS 2712:2007 Solar and heat pump water heaters – Design and construction

Provides performance-based design and construction requirements for solar hot water systems. It applies to

both components and complete systems, for residential, commercial and industrial installations.

It requires that instructions in English on installation and maintenance should be supplied, complete with

appropriate diagrams and other relevant information. Operating and maintenance instructions should also

be supplied to the householder with each water heater.

AS/NZS3500.4:2003 Plumbing and drainage – Part 4: Heated water services

Refers to thermal insulation requirements for storage water heaters. Piping should be thermally insulated to

achieve the minimum R-value for the specific climate region. Insulation exposed to the weather should be

weather-resistant or surrounded by a weather-resistant enclosure.

AS/NZS 4234:2008 Heated water systems - calculation of energy consumption

Covers the computation from physical test results, proprietary information, known component properties

and weather data of the expected annual performance of a range of water heaters including conventional

solar and heat pump water heaters. The computation is based on a particular modelling software package,

known as TRNSYS.

AS/NZS 4445.1:1997 Solar heating – Domestic water heating systems – Part 1: Performance

rating procedure using indoor test methods

States that tests should be carried out with the system components installed according to the manufacturer’s

installation instructions. It gives testing instructions for those systems that do not have manufacturer’s

instructions. The method covers all requirements for system installation, measurement and test procedures.

AS/NZS 4552.2:2010 Gas fired water heaters for hot water supply and/or central heating –

Part 2: Minimum energy performance standards for gas water heaters

Specifies minimum energy performance standards requirements for gas water heaters up to a nominal gas

consumption of 50MJ/h for storage types and 250MJ/h for instantaneous types. The MEPS is a maximum

allowable annual energy consumption requirement.

Appendix 1: Standards


AS/NZS 4692.1:2005 Electric water heaters – Part 1: Energy consumption, performance and

general requirements

Includes performance test procedures, minimum performance requirements and other water heater

requirements. Includes the revised test method for ESWH standing heat loss, as well as the test method for

hot water delivery.

AS/NZS 4692.2:2005 Electric water heaters – Part 2: Minimum Energy Performance

Standard (MEPS) requirements and energy labelling

Includes minimum energy performance standards (MEPS) for ESWHs. Is to be used in conjunction with

Part 1.

Australian standards

AS 1056.1-1991 Storage water heaters – Part 1: General requirements

Specifies requirements for storage water heaters heated by electricity and gas storage water heaters. These

requirements cover construction, electrical components, installation and compliance.

AS 1056.2-1985 Storage water heaters – Part 2: Specific requirements for water heaters with

single shells

Specifies requirements for water heaters with single shells made from plastics, non-ferrous metal or stainless

steel. Covers aspects such as materials, thickness, protection against corrosion and welding.

AS 1056.3-1991 Storage water heaters – Part 3: Specific requirements for water heaters with

composite shells (SUPERSEDED BY AS/NZS 4692.1)

Specifies requirements for water heaters with composite shells made from steel and protected with a metallic

insert, a bonded vitreous enamel lining or a bonded plastics lining.

AS 1361-1995 Electric heat-exchange water heaters – For domestic applications

Specifies requirements for electric heat-exchange water heaters with a heat-storage volume of 45L to 710L,

which heat potable water at mains pressure for domestic applications.

AS 2984-1987 Solar water heaters – Method of test for thermal performance – Outdoor test

method (NOW OBSOLETE)

Sets out a method for testing a solar water heating system under natural outdoor conditions. The results from

the testing are able to be transformed to long-term average conditions for similar solar irradiation

conditions. The systems tested must be an auxiliary heating system that can satisfy the load under no-solar

input conditions.

AS 3498-2009 Authorisation requirements for plumbing products – Water heaters and hot-

water storage tanks

Covers the basic safety and public health requirements for water heaters. It specifies the minimum exposure

period required to inhibit the growth of legionella bacteria within the water-heating appliance.

AS 4552-2005 Gas fired water heaters for hot water supply and/or central heating

Covers requirements for gas water heaters and central heating boilers, including design and construction,

maintenance, safety and gas testing. Includes many methods of test.

New Zealand standards

NZS 3604:2011 Timber-framed buildings

Sets out construction requirements for timber-framed buildings. This is only necessary if the storage tank

will be located on the roof.


NZS 4614:1986 Installation of domestic solar water heating systems

Covers installation of systems of fixed orientation and inclination of up to 6m2 collector area and 450 L

storage capacity, capable of auxiliary heating and delivering potable water, but excluding space or pool

heating.

International standards

A 2011 CLASP study found that generally, international standards for water heating appliances are poor or

non-existent.

There has been an agreement to develop a common EN/ISO 9806 standard for solar collectors testing

methods as a step towards global certification for solar collectors. A draft of this standard has been developed

and released for consultation (ESTIF, 2012).

The only international standards that are directly relevant to SWHs are a series of ISO standards that were

initially developed for SWHs, but which have the potential to be adapted for other water heater technologies.

The relevant international SWH standards are:

• ISO 9459-1:1993 - Solar heating -- Domestic water heating systems -- Part 1: Performance rating

procedure using indoor test methods

• ISO 9459-2:1995 - Solar heating -- Domestic water heating systems -- Part 2: Outdoor test methods

for system performance characterization and yearly performance prediction of solar-only systems

• ISO 9459-5:2007 - Solar heating -- Domestic water heating systems -- Part 5: System performance

characterization by means of whole-system tests and computer simulation

• ISO/CD 9459-4 - Solar heating -- Domestic water heating systems -- Part 4: System performance

characterization by means of component tests and computer simulation


There have been both State and Territory and Australian and New Zealand government rebates and

incentives for the purchase and installation of solar water heaters, however most have now closed.

Australia

The availability of Commonwealth and state and territory government SWH rebates had a large impact on

the Australian SWH market. This effect is now greatly reduced, with the cessation of the Commonwealth and

most state and territory schemes. Energy certificate schemes have also had an impact on the Australian SWH

market, including STCs.

Commonwealth of Australia

The Federal Government offered rebates for SWHs in various forms from July 2007 until June 2012.

The Australian Government Solar Rebate program was available from July 2007 to February 2009 and

provided a $1,000 means tested solar water heater rebate for eligible households to install a solar water

heater or heat pump water heater to replace an electric resistance water heater.

This was replaced by the Solar Hot Water Rebate in February 2009, which offered $1,600 for installation of

an eligible solar or heat pump water heater to replace an electric resistance water heater.

The Renewable Energy Bonus Scheme (REBS) ran between February 2010 and June 2012. REBS offered

rebates of $1,000 for SWHs that replaced existing conventional electric water heaters in existing private

homes. To be eligible for a REBS rebate, systems needed to be eligible for at least 20 STCs, which was

difficult to achieve with small SWHs, as small systems produce less renewable energy/ displace less

electricity than larger products of equal efficiency.

Together these rebate programs provided 255,000 rebates in excess of $323 million.

Small-scale technology certificates

Under the Small-scale Renewable Energy Scheme (SRES), eligible SWHs are entitled to a number of small-

scale technology certificates (STCs). The number of STCs received depends on the amount of electricity the

system is estimated to produce or displace over its lifetime (assumed to be 10 years).

STCs can be assigned to a registered solar Agent (such as a retailer or installer) in exchange for a financial

benefit to the consumer, such as a discount off the purchase invoice. SWHs typically create around 20 to 30

STCs and so generally create a reduction in the up-front cost to the consumer of around $800 to $1,00025.

The 2012-13 annual report by the Clean Energy Regulator stated that from January 2011 to 30 June 2013

1,876,870 valid small scale installations had been registered including 644,994 SWHs. While it is difficult to

proscribe a value against this support due to the nature of the underlying, market-driven price, conservative

estimates place the value of STCs provided to for SWH as at June 2013 around $500 million.

Australian states and territories

All Australian states and territories have had some kind of SWH rebate or incentive scheme in place in the

recent past, with only Victoria, South Australia and the Northern Territory having schemes still running. The

state and territory schemes varied widely in terms of eligibility, value of rebate, length of scheme and overlap

with other rebates and incentives.

For details on the state and territory SWH rebates and incentives see Table 15.

25 It is noted that the value of STCs can vary over time, and therefore, the value of rebates over the life of the program has varied and will

continue to do so.

Appendix 2: State and territory rebates


State Program Program

Dates

Description Eligible

Households

New South

Wales

NSW Home

Saver Rebate

1 October 2007

to 30 June

2011

A $600 rebate was available

for a solar water heater eligible

for at least 20 STCs, and up to

$1,200 for models eligible for

43 or more STCs. In January

2010, the amounts were

equalised at $300 for all types.

Households that

replaced an electric

storage water heater

with a new gas, solar

or heat pump water

heater.

Victoria Victorian

Government

Solar Hot

Water Rebate

Scheme

October 2007

(metro)/June

2008

(regional) to 31

May 2013

Comprised of two rebate

programs – the metropolitan

rebate ranged from $300 to

$1500, while the regional

rebate ranged from $400 to

$1600. For the replacement of

electric water heaters with

solar-electric, and gas with

solar-gas water heaters. An

additional $200 was available

for a new gas connection to the

property.

Households that buy

an eligible

replacement solar

water heater from a

supplier registered

with Sustainability

Victoria.

Victorian

Government

Solar Hot

Water Rebate -

Bushfire

Affected

Homes

28 February

2009 to 31 May

2013

Up to $1600 is available to

assist bushfire-affected

homeowners replacing a gas or

non-electric water heater with

a gas boosted solar hot water

system in their new home.

Households whose

residence was

destroyed in the 2009

Victorian Bushfires

and are eligible to

receive a Destroyed

Homes Payment

through the Victorian

Bushfire Appeal

Fund.

Victorian

Energy

Efficiency

Target

1 January 2009

to current

Accredited businesses are able

to create Victorian Energy

Efficiency Certificates from

assisting households to make

energy efficiency

improvements, including

through the sale and

installation of a solar water

heater. The benefit of the

VEECs is passed onto the

consumer as a discount on the

purchase price of their system.

Householders who

purchase an approved

water heating product

through a VEET

accredited business

and have it installed

by them.

Queensland Solar Hot

Water Rebate

1 July 2009 to

22 June 2012

A $1000 concessional rebate

for pensioners and low income

earners, and a $500 standard

rebate for all other households.

This was standardised to $600

for all households from 13

April 2010.

Households that

replaced an electric


with a solar or heat

pump water heater.


State Program Program

Dates

Description Eligible

Households

South

Australia

Solar Hot

Water Rebate

Scheme

1 July 2008 to

30 June 2013

A rebate of $500 is available to

low income households, for the

installation of a solar water

heater or heat pump.

Householders must

have an eligible

Australian

Government

concession card.

Residential

Energy

Efficiency

Scheme

1 January 2009

to 2020

Energy retailers with 5,000 or

more electricity or gas

residential customers are

required to provide incentives

for households to reduce

emissions and lower their

energy use, including

upgrading or replacing a water

heater with a gas, solar or heat

pump water heater.

All South Australian

households.

Western

Australia

WA Solar

Water Heater

Subsidy

Scheme

June 2005 to 1

June 2013

A rebate of $500 for natural

gas boosted solar water heaters

and $700 for LPG boosted

solar water heaters.

Households that

replaced their electric


with a gas boosted

solar water heater

with a storage tank of

at least 250L.

Tasmania Hobart City

Council Solar

and Heat

Pump Water

Rebate

1 July 2007 to

30 June 2013

(solar)

A $500 rebate for installing a

solar water heater or heat

pump to replace an electric

storage water heater.

The system installed

must replace an

electric storage water

heater, have a

minimum of 20 STCs

and be installed

within the City of

Hobart.

Northern

Territory

Solar Hot

Water Retrofit

Rebate

28 June 2009

to current

Power & Water Corporation

are providing a rebate of up to

$1000 for homes with timber

trusses and up to $400 for

homes with steel trusses.

Homes must have

been built in or before

2000 and the solar

water heater must be

replacing an electric

storage water heater.

Australian

Capital

Territory

Home Energy

Advice Team

(HEAT)

Energy Audit

Closed 20 April

2013

The ACT Government will

provide a $500 rebate on

expenditure of $2000 or more

on priority recommendations

from a HEAT Energy Audit.

Households that had

a HEAT energy audit

performed and spent

an extra $1,000 on

other household

energy saving

improvements.

Table 15: Summary of Australian state and territory SWH rebates

New Zealand

The New Zealand Government began to provide financial support for SWHs in 1978, through the provision of

interest-free loans for the purchase and installation of approved SWHs. By 1982, an estimated 6,500 SWHs


had been installed in New Zealand, with over half of these funded by the loan scheme (PCE, 2012). The

scheme continued until 2000, despite low uptake rates and poor electricity savings of the SWHs (PCE, 2012).

EECA provided a subsidy of $300 for SWHs from 2002. In 2008, this amount was increased to $500, with

high efficiency models receiving $1,000. The subsidy was reviewed in 2011 and it was announced in the 2012

Budget that it would cease in June 2012. From 2007 to 2013, 10,200 SWHs have been installed with EECA

grants (EECA 2013).

Local councils are involved in the SWH market, where some councils subsidise building consent fees, and a

few offer loans for SWHs to be paid back with rates.


There are a wide range of ways that manufacturers may present or express similar types of information.

Examples of how claims in these areas are expressed by manufacturers include:

• Energy savings:

— ‘can save up to x% of water heating consumption’

— ‘provides x% of household hot water needs’

— ‘uses up to x% less energy than an electric water heater’

— ‘use up to x% less energy than conventional water heaters’

— ‘reduces energy use by up to x%’

— ‘substantial savings on your household water use’

— ‘energy free from the sun’

• Frost resistance levels:

— ‘protected against freeze damage up to x degrees’

— ‘offers true frost protection’

— ‘suitable for down to x degrees’

— ‘multi-flow closed circuit operation makes it suitable for frost prone areas’

— ‘frost tolerant for temperatures down to x degrees’

— ‘features drain-back heat exchange technology, which prevents freezing’

— ‘suitable for frost prone areas’

• Solar collector performance:

— ‘peak collector output is approximately x kW’

— ‘maximum temperature rise is approximately x degrees at the maximum flow rate’

— ‘collectors have amazing thermal absorption qualities’

— ‘high efficiency collectors to absorb the maximum available solar energy’

— ‘multi-rise collectors efficiently absorb energy from the sun

Appendix 3: Manufacturers’ claims


Manufacturers’ claims on tested electric boosted solar water heaters

Table 16: Manufacturers claims on tested electric boosted solar water heaters

Electric boosted SWHs

Model Energy savings – Online claims Tested results STCs claims Greenhouse

gas emissions

Other claims Associated test

result

E1

(SE250)

Not available -3-39%

25% in Zone 3

Not available Not available

E2

(SF415)

Not available 52-88% Not available Not available Outstanding efficiency to help

reduce energy bills

High performance black chrome

selective surface collectors

Had fairly high

collector

efficiency

E3

(SF270)

Cuts energy use by up to 70% (Energy

reduction based on Australian

Government approved TRNSYS

modelling. Apply when replacing an

electric water heater with this brand’s

solar water heater in zone 3).

47-83%

60% in Zone 3

Not available Reduces

greenhouse gas

emissions

Choice of 6-star gas boost or

electric element backup to

provide hot water in any

weather condition.

E4

(SF325)

Save 55% to 85% of your water heating

energy consumption. (Savings based on

Australian Government approved

TRNSYS modelling. Savings vary

depending on location, type of system

installed, orientation and inclination of

solar collectors, type of water heater

replaced, hot water consumption and

fuel tariff.)

47-83% Not available Reduced energy

use saves up to

3.3 tonnes of CO2

emissions every

year

Hot water regardless of the

weather

Toughened, hail resistant

collector glass

Passed collector

impact resistance

test


E5

(SE340)

Save up to 80% on your water heating

bills

16-79%

56% in Zone 3

Not available Reduce your

household carbon

emissions

Produce free hot water from the

sun

E6

(TF305)

Not available 48-87% Not available

E7

(TF330)

Not available 55-89% High STCs

awarded for each

system.

Zone 1 – 40 STCs;

Zone 2 – 43 STCs;

Zone 3 – 39 STCs;

Zone 4 - 34 STCs

Minimised heat loss and

maximised efficiency.

Low heat loss due to greater

insulation.

Technically very efficient and

low maintenance.

High efficiency collectors absorb

the maximum available solar

energy.

Frost protection to -6 deg C.

Tank would not

meet maximum

allowable heat

loss if ESWH tank

heat loss MEPS

was applied.

Had high

collector

efficiency.

System was not

declared as frost

protected and

failed the frost

resistance test.

E8

(TF300)

You can cut your water heating energy

consumption by up to 90% in the hotter

parts (Zone 2) of the country, up to 75%

in the temperate parts (Zones 1 & 3) and

up to 60% in the cooler parts (Zone 4).

Zone 1 – 84%

Zone 2 – 89%

Zone 3 – 65%

Zone 4 – 49%

Not available Reduced energy

use saves up to

3.5 tonnes of CO2

emissions every

year.

Specifically designed to provide

higher efficiency for use in low

to medium solar gain areas.

Hot water regardless of the

weather.

Boost capacity 150L.

Higher efficiency absorber

maximises the absorption of

available solar energy.

Suitable for frost-prone or poor

water chemistry areas.

Had high

efficiency

collector.

System was

declared frost

protected but

failed the frost

resistance test.


Manufacturers’ claims on tested gas boosted solar water heaters

Table 17: Manufacturers’ claims on tested gas boosted solar water heaters

Gas boosted SWHs

Model Energy savings – Online claims Tested

results

STCs claims Greenhouse

gas emissions

Other claims Associated

test result

G1

(TI180)

Reduces energy use by up to 85% (Energy

reduction up to 73% based on Australian

Government approved TRNSYS modelling.

Applies when replacing an electric water

heater in Zone 3. Energy savings of up to

85% based on Zone 1 modelling.)

54-77%

Zone 1 – 68%

Zone 3 – 62%

Not available Not available Complete frost protection

G2

(TI305)

Not available 57-84% Not available Not available Not available

G3

(SI165)

Cuts energy use by up to 60%. (Savings

based on Australian Government approved

TRNSYS modelling in zone 3. Savings will

vary depending on your location, type of

system installed, type of water heater being

replaced, hot water consumption and fuel

tariff.)

55-84%

Zone 3 – 67%

Zone 1 – 13 STCs

Zone 2 – 15 STCs

Zone 3 – 13 STCs

Zone 4 – 11 STCs

Lower greenhouse

gas emissions

Nominal gas consumption 199 MJ/hr Determined

gas

consumption

210.9 MJ/hr

G4

(SI215)

Not available 55-87% Zone 1 – 38 STCs

Zone 2 – 42 STCs

Zone 3 – 38 STCs

Zone 4 – 33 STCs

The higher the

STCs awarded,

the more solar

savings a system

Assists with the

reduction of our

carbon footprint.

Minimised heat loss and maximised

efficiency.

Gas or electric booster ensures that

you will never run out of hot water.

Tanks exceed the MEPS

Tank would

not meet

maximum

allowable

heat loss if

ESWH tank

heat loss

MEPS was

applied.


Gas boosted SWHs

offers. This

brand’s systems

have amongst the

highest STCs in

the industry.

G5

(SS322)

Not available 51-77% High STC values.

Has one of the

highest STCs

when compared

to similar systems

– meaning more

savings for you.

Zone 1 – 38 STCs

Zone 2 – 42 STCs

Zone 3 – 35 STCs

Zone 4 – 31 STCs

(STC calculations

for gas boosted

units are based on

continuous tariff.)

Environmentally

friendly.

Greenhouse gas

emissions = 0.20

tonnes per annum

Superior efficiency. High efficiency

polyurethane insulated storage tank.

Low mega-joule consumption

burner. Gas consumption = 45MJ/hr

Running cost per annum =$36

1st hour delivery at 40oC=780L

Continuous mains pressure hot water

on demand. Guaranteed hot water in

24 hours.

Zero water wastage during start-up

cycle.

Solar management system protects

the system from overheating in

summer and provides frost

protection in winter.

Determined

gas

consumption

45.2 MJ/hr


Gas boosted SWHs

G6

(TS300)

Can save up to 50% to 85% of water heating

energy consumption.

(Savings based on Australian Government

approved TRNSYS simulation modelling

using a medium load. Savings and

incentives will vary depending upon your

location, type of system installed,

orientation and inclination of the solar

collectors, type of water heater being

replaced, hot water consumption and fuel

tariff.)

59-86% Reduced energy

use can save up to

1.9 to 3.0 tonnes

of CO2 emissions

per annum.

Specifically designed to provide

economical service in medium to

high solar gain areas.

Reliable, low maintenance operation.

Hot water regardless of the weather.

Boost capacity 150L.

Not recommended for use in frost or

poor water chemistry areas.


This chapter provides some additional test results and discussion not covered in Chapter 6. These additional

results have been placed in this Appendix as they provide useful insights into the performance of SWH, but

the results are either too complex or lengthy to include in the body of this report.

Many of the test reports and discussion make reference to climate zones and a simple map is provided below

to depict these zones.

Figure 34: SWH climate zones for Australia26 and New Zealand

Source: AS/NZS 4234:2008

Additional results on tank heat loss

As SWHs are either excluded or not subject to the ESWH heat loss MEPS requirements, the design of their

tanks is not optimised for the requirements in AS/NZS 4692.2. Several storage tanks had a measured hot

water delivery slightly below a specified MEPS ‘step’, which meant that they were assessed against a lower

step with tighter tank heat loss requirements. Being just 1 litre under a MEPS ‘step’ threshold effectively

penalises such systems by requiring a far more stringent heat loss requirement than if the systems was 1 litre

larger. Figure 35 shows the standing heat loss results after some systems were adjusted to the closest MEPS

step. While the results of Figure 35 are not strictly in accordance with the Standard, the results probably give

a ‘fairer’ indication of how these tanks compare to the heat loss requirements which ESWH must meet.

26 Contour lines show annual average daily solar radiation (MJ/m2)

Appendix 4: Test results


Figure 35: SWH tank heat loss compared to MEPS level for ESWHs (adjusted to closest MEPS step)

Even with some tanks being provided adjustments over and above what the Standard would strictly allow,

the majority of SWHs tested have heat loss levels worse than the minimum level allowed for a conventional

electric water heater. This reduces the ability of a SWH to store heated water over long timeframes when

solar irradiation levels are low.

Additional information on heat loss and air temperatures

The product profile notes that the current heat loss tests are conducted in 20°C conditions. The profile also

notes that the majority of the Australian and New Zealand population live in conditions colder than 20°C. So

for consumers in these areas with an externally located hot water storage tank, the actual level of heat loss

experienced will be higher than what the Standard test results imply.

It is very important to note that any Standard test must prescribe conditions such as air temperature so that

test results can be accurately reproduced by any accredited test laboratory. Setting the required air

temperature at 20°C means that it is easier (and cheaper) for a laboratory to set and maintain these

conditions –with savings ultimately passed on to consumers. The test results may not be accurate to average

‘real-world’ results, but the results between systems can be compared. A tank that performs ‘better than

average’ at 20°C, will also perform ‘better than average’ at other temperatures. So the results can provide

comparative information but are less useful in informing consumers of likely running costs. The test results

should be used with care in any modelling or calculation of running costs

AS/NZS 1056.4 has a number of useful formulae that can be used to ‘convert’ test results at 20°C to other

temperatures. The formulae are complex and depend on factors such as the tariff a system is connected to

and the location or presence of key fittings on the tank. However a simplified form of the formulae is

presented below.

Energy Used = Energy demanded * Expansion loss factor +

(Actual thermostat

temp minus actual air

temp) * Tank heat loss

test result (Thermostat temp

minus air temp used

during heat loss test)


The results of these calculations show that in a tank with a thermostat temperature of 75°C the energy used

will be 9% more energy at 15°C than 20°C and 18% more at 10°C. In cold conditions, such 0°C, energy use is

36% higher – and it is in cold conditions that a SWH will generally have a higher reliance on boosting. For a

system with a 60°C thermostat setting the percentage differences are greater – 13% more energy at 15°C, 25%

more at 10°C and 50% more at 0°C compared to a 20°C test.

Additional data on system heat loss and energy savings

The results of the tank and system heat loss testing were used as inputs for TRNSYS modelling of annual

energy savings for three systems. The modelled results show that there was some difference in annual energy

savings between using the tank or system heat loss as input into the model. Two systems were modelled as

stratified tanks and show an energy savings difference of approximately 2% within each climate zone, whilst

the third system was modelled as a mixing tank with an energy savings difference of approximately 5% within

each climate zone. Using tank heat loss as the heat loss input gave higher energy savings than using system

heat loss.

The extra heat loss of 0.49kWh per 24 hours would cost approximately 15 cents per day in Australia or

13 cents per day in New Zealand27 if reheated using a conventional electric storage water heater. If we

assume that an electric boosted SWH provides an average 60% annual energy saving, and only uses

electricity for 40% of its energy needs, this difference in heat loss between SWH tanks and systems would

cost approximately $22 per year in Australia or $19 per year in New Zealand. These are the costs that are not

disclosed to the user under the current approach of only using tank heat loss as a data input rather than the

more realistic system heat loss figure.

Figure 36: Difference between using tank and system heat loss to model energy savings for electric

boosted SWHs

Field test results for Model E1

Three field test scenarios were performed by this project with Scenario 2 being based on the AS/NZS 4234

hot water usage patterns used for energy modelling. During this test Model E1 performed very poorly, using a

similar amount of energy as a conventional electric system. A snapshot of how Model E1 performed over a

24-hour period is provided at Figure 37.

27 Based on the 2012/13 average national electricity tariff of AU29.6c/kWh in Australia and NZ26.3c/kWh in New Zealand.


Figure 37: Energy use and system temperatures for Model E1 over a 24-hour period

The key parameters to observe in Figure 37 is the black line, which shows electrical power consumption (i.e.

booster operation) and the yellow lines which indicate when hot water was drawn from the SWH. The graph

shows that the booster switched on at approximately 1am and 6am, before any hot water had been drawn-off.

A SWH that boosts multiple times at night in ‘mild’ conditions and when no hot water is being used shows

poor ability to store heated water. It is also important to note that the tank heat loss test result for this system

was good, so there is an unidentified system or design flaw that is leading to this additional energy usage.

The performance of the system during the day was better. The booster was needed when hot water was

demanded in the early morning and the evening, but the hot water demanded during the middle of the day

did not trigger the booster as solar gain had sufficiently heated the stored water.

As over the month long test the SWH used a similar amount of energy as a conventional electric system, we

can conclude that the energy savings observed by the tank not needing boosting during the middle of the day

were effectively balanced out by additional ‘unwarranted’ boosting at other times. As such significant

‘unwarranted’ energy usage will not have been noted in the manufacturer’s TRNSYS energy savings

calculations and claims, we can see the negative impact of only including some component test results in the

energy savings model or not double checking the model outputs with an actual physical test.


Additional data on the Scenario 2 field tests

Figure 38: Cumulative water delivered for Scenario 2

Figure 38 shows that all three SWHs and the reference conventional electric water heater delivered very

similar amounts of hot water. However, as seen in Figure 39, when hot water delivery is looked at in terms of

percentage of tank size, there are significant differences in delivery between the three SWHs.

Model E1 provided almost 130% of the tank volume daily, while Model E8 provided approximately 110% of

tank volume and Model E2 provided just under 80%. This occurred as all SWHs were subject to the same hot

water load demand so that comparative results could be produced. Model E1 used substantially more

electricity to deliver its 130% load.

Figure 39: Average daily hot water delivery and element energy use for Scenario 2 testing


Additional data on the field tests

While the lack of electrical energy available for boosting in Scenario 3 had an effect on the ability of the

systems to deliver hot water, the lower availability of solar energy also had a significant effect. Scenario 3 had

lower solar irradiance and ambient temperature than Scenarios 1 and 2. Lower solar irradiance and ambient

temperature generally result in lower tank temperatures and a lower ability to provide large amounts of hot

water without relying on boosting.

Figure 40 shows that the amount of solar irradiance decreased for each stage of testing. There was a 37%

reduction in cumulative irradiance between Scenario 1 and 2 testing and a 24% reduction between Scenario 2

and Scenario 3. The ambient temperature also decreased for each scenario– Scenario 1 had an average

ambient temperature was 22°C, Scenario 2 was 19°C and Scenario 3 was 15°C.

Figure 40: Cumulative irradiance for all three scenarios

The test standard for solar collectors (AS/NZS 2535.1) requires for the outdoor test that solar irradiation is

greater than 800W/m2 (0.8kW/m2). However, this test is based around assessing the collector during a

period of high solar irradiation (e.g. noon) and it is difficult to compare this to the conditions in the month

long test which includes night periods and low irradiation periods (early morning and evening). If 500MJ/m2

of cumulative irradiance occurred over a 30 day period, this is an average of 16.7 MJ/m2 per day or

4.6kWh/m2. It would take 5.75 hours of irradiation being supplied at 0.8kW/m2 (the minimum standard

level) to provide 4.6kWh/m2. While this comparison should be treated with a high degree of caution, it does

hint that the tests generally had high or acceptable levels of irradiation being supplied on average.

Additional data on pipe insulation and pipe length

TRNSYS modelling to AS/NZS 4234 was conducted for all of the electric boosted SWHs to determine their

sensitivity to changes in insulation thickness and pipe length between the tank and collector. As these pipes

carry the solar heated water from the collectors to the tank, their length and level of insulation has an

important effect on how effectively a solar collector can heat a water storage tank.

Pipe insulation modelling for split systems was performed for insulation thicknesses of 9mm, 13mm and

19mm in climate zones 3 and 5 for a pipe length of 10 metres. The three systems with flat plate collectors had

less than a 1% difference in energy savings between all pipe insulation thicknesses in both climate zones,


whereas the two systems with evacuated tubes had energy savings differences of up to 6% when comparing

9mm to 19mm insulation.

The results of the insulation thickness modelling show that the thickness of pipe insulation is a material

consideration especially in colder areas, for split systems and for systems that utilise evacuated tube

collectors.

Figure 41: Sensitivity to variation of pipe insulation thickness for electric boosted split systems

The length of pipes between the storage tank and solar collector for split systems were also modelled. The

pipe lengths in a split system will vary depending on tank location, collector location and building height.

Greater pipe lengths corresponded with decreased energy savings, with systems with evacuated tubes having

a much more noticeable difference in energy savings.

The three flat plate collector systems modelled had approximately 2% difference in energy savings between

5m and 15m pipe lengths in both climate zones. The two evacuated tube collector systems were much more

affected by changes in pipe lengths, with an average 9% difference in energy savings for Model E5 and an

average 15% difference for Model E1 between 5m and 15m pipe lengths.


Figure 42: Sensitivity to variation in pipe length for electric boosted split systems

The results of the pipe length testing demonstrated the preference to locate a storage tank as close to the

collectors as feasible, but the importance of this for the evacuated tube systems was far greater. This

preference also needs to be weighted up against the preference to locate collectors in the section of the roof

receiving the most solar irradiation.

Pipe insulation modelling for thermosiphons was performed for insulation thicknesses of 9mm, 15mm and

19mm in climate zones 3 and 5, as shown in Figure 43. The change in energy savings is largely immaterial

which reflects the small pipe lengths that thermosiphons generally have.

Figure 43: Sensitivity to variation of pipe insulation thickness for electric boosted thermosiphons


Collector test results

All eight of the collectors were tested to the indoor efficiency test method as it is more reliable and consistent

than the outdoor efficiency test method. However, the outdoor efficiency test is cheaper to perform, as it

requires less specialised equipment. Three of the collectors were also tested using the outdoor test method, to

provide a comparison between the two tests.

TRNSYS modelling was conducted for the three collectors that were tested to both the indoor and outdoor

test method, to compare differences in the annual energy savings due to the different test methods. The

results, as seen in Figure 44, showed very small differences in annual energy savings between the indoor and

outdoor test modelling, ranging on average from 0.5% to 1.5%.

These test results indicate that it makes very little difference to modelled energy savings if the collector tests

are performed indoors or outdoors.

Figure 44: Modelled difference in energy savings between indoor and outdoor collector tests28

Additional data on collector freeze testing

A summary of freeze test results is provided in the body of the Product Profile. Detailed information on the

results of the collector freeze tests for each of the collectors is provided below.

Model E3 (SF270) was not declared as a frost protected system, but the freeze test showed that it does have a

response built in to help protect against freezing. A circulation pump is programmed to switch on when the

water in the collector drops to 4oC or below and not switch off until the water is 6oC or higher – heated from

the hot water in the storage tank.

The collector was subject to the Standard collector freeze test (Figure 45) and the data shows that the

circulation pump switched on and off a number of times during the first of six required freeze cycles before

the pump failed to prevent freezing of water in the collector, which lead to a burst pipe and failure of the

system. This shows that the pump was able to mitigate some of the ‘freezing’ but was overwhelmed. It is

worth noting that Model E3 was tested with two collectors as this is how the system was sold. As the

Standard only requires that one collector needs to be subject to a freeze test, the pump may have been able to

provide adequate protection in the test environment – highlighting the need to conduct such tests with as

many collectors as a system is sold with.

28 Reasons for poor modelled energy savings for Model E1 are discussed in the modelled energy savings section of the test results.


Figure 45: Model E3 (SF270) freeze test results

Similar to Model E3, Model E4 was not declared as a frost protected system, but showed in the freeze test

that it has a method of frost protection programmed into the circulation pump, with the pump also switching

on when the water in the collector is at 4oC and off at 6oC. The circulation pump switched on in response to

the temperature falling below 4oC in the first cycle. However, it appears that the pump response to switch off

when there are small differences between tank and collector temperatures overrides the frost protection

control and the pump did not switch on in any further freeze cycles. The water temperature in the collector of

Model E4 cooled gradually over each freeze cycle until it froze on the fifth cycle, which led to blockage and a

burst pipe in the collector.


Model E6 is a thermosiphon, which means it doesn’t have a circulation pump to use as a frost protection

method and also that the storage tank was located inside the test chamber for the freeze test, whereas split

systems had the storage tank located outside the test chamber. Locating the storage tank inside the test


chamber exposes the storage tank and associated pipework to higher potential heat loss than for systems that

have the storage tank outside the test chamber, which increases the risk of freezing and system failure. The

temperature of water in the collector fell very quickly during the first freeze cycle and wasn’t able to recover

due to the lack of a circulation pump. The temperature fell further during each freeze cycle until it reached

approximately -11oC in the fifth freeze cycle, which resulted in the pipe bursting in the collector.

The test clearly demonstrates that a thermosiphon loses energy during freezing conditions, however

AS/NZS 4234, used for energy savings modelling, appears to only assume pumped, open circuit (water)

SWHs lose energy. This means the performance of thermosiphons in colder areas will be overstated.

Figure 47: Model E6 (TF305) freeze test results

Model E7 is also a thermosiphon and so did not have a circulation pump to act as a frost protection method.

The temperature of water in the collectors of Model E7 fell very quickly in the first freeze cycle until it got

below zero degrees and the water froze. This freezing in the first freeze cycle caused the pipe inside the

collector to burst, which resulted in water leaking inside the collector and the system failing.



Model E8 is a freeze protected model, but as it is a thermosiphon, it’s not able to use fluid circulation as frost

protection. Model E8’s frost protection was the use of glycol as a heat transfer fluid. The use of glycol

prevented freezing within the pipes and the system was able to function over the six freeze cycles. Before the

test and at the completion of the final cycle, the tank was subjected to a typical pressure test29. No leaks were

detected before the freeze testing. However, when the system was subjected to pressure testing after

completion of the final freeze cycle, a leak was detected from the electric element end of the tank and in the

absorber plate of the collector, closest to the collector inlet pipe. This means that the system was damaged by

the freeze test and as a result it is classed as failing.

Again the water temperature inside the storage tank can be seen to drop, despite the assumption in

AS/NZS 4234 that thermosiphons do not seem to loose energy from freeze conditions. AS/NZS 2712 also

states that freeze resistance can be assumed (no test needed) if the fluid in the collector either does not

expand when frozen or is capable of flowing (not freezing) at -15°C. It is very likely that this collector could

use one of these exemptions and could be sold without conducting a physical freeze test.

29 The applied pressure was twice that of the tank pressure relief valve.



Model E2 was one of the few systems to successfully pass the freeze test. Model E2 was not declared as a frost

protected system, but the freeze test showed that it has two methods of frost protection. Its first method of

frost protection is programmed into the circulation pump, with the pump also switching on at 5oC and off at

9oC. The circulation pump switched on in response to the temperature falling below 5oC in the first and

second cycles, however it appears that the pump response to switch off when there are small differences

between tank and collector temperatures overrides the frost protection control and the pump did not switch

on in any further freeze cycles.

Model E2 also has a frost protection valve, which is the second form of frost protection. The frost protection

valve was operating throughout the test, with the majority of water discharged in the later freeze cycles. The

temperature of the frost protection valve is an indication of how much water was discharged over the test

period. Higher frost valve temperatures indicate that water is discharged from the valve. Approximately 220L

of water was discharged from the frost valve during the freeze test.

Figure 50 shows that the system was able to keep collector temperatures either above or very close to 0oC and

prevent freezing and damage to the system.



Model E1 was a declared frost protected system that successfully passed the freeze test. Its method of frost

protection was through the circulation pump, which switched on when the collector water temperature was

at 4°C and off at 6°C. Figure 51 shows that the circulation pump was cycling on and off during the freeze

cycles in order to keep water circulating and prevent freezing. A blockage occurred in the fourth freeze cycle,

which prevented the pump from circulating water and resulted in the temperature in the collector dropping.

Even though the apparent freezing and blockage didn’t cause the system to fail, it raises concerns about if the

system could resist failure if such freezing was to occur repeatedly – as would occur in real life conditions.

Viewing any test which involves a freeze blockage as a failure would help ensure that only solar collectors

likely to survive many freeze cycles would be sold into cold areas.

The long warm cycle in the middle of the test was due to issues with the test chamber.

Figure 51: Model E1 (SE250) freeze test results


Model E5 was also a declared frost protected system that successfully passed the freeze test. Its method of

frost protection was through the circulation pump, which switched on when the collector water temperature

was at 4oC and off at 5oC. The circulation pump switched on and off in each freeze cycle and managed to keep

the temperature inside the collector above 0oC.

Figure 52: Model E5 (SE340) freeze test results

Additional data on freeze tests and energy savings modelling

To test the accuracy of TRNSYS modelling at low temperatures, the collector freeze tests were replicated in

the TRNSYS model. The modelled results were then compared against actual observations of SWH

performance under freeze conditions.

The TRNSYS modelling output for Model E4 had some errors in the first cycle, due to issues with test

measurements that were fed into the model. However, from the end of the first cycle, the model shows that

each cycle follows the same pattern, where the water temperature in the collector falls far below 0oC in each

freeze cycle and then cycles between approximately 5 and 15oC as the pump switches on and off.

The TRNSYS modelling output for Model E5 shows that the water temperature in the tank and collector

decreases very slowly and follows the same pattern over the six freezing cycles. The tank and collector

temperatures decrease by the same amount over each freeze cycle and increase by the same amount over

each warm cycle.

In Figure 53, it can be seen that for Model E4, the pump switched on during the first freeze cycle, while

Figure 52 shows that the pump was working during every freeze cycle of Model E5’s test. Pump operation will

slightly increase the energy use of the system, but it also helps to try and keep the water temperature inside

the collector above 0oC and prevent freezing of the system.

It will also affect the heat loss of the system and hot water availability to the consumer, as circulating warm

water from the tank to the collectors and cold water from the collectors to the tank will decrease the average

tank temperature and likely result in higher heat loss from the collector.

There are several issues with the TRNSYS freeze modelling. The TRNSYS model assumes that water is always

liquid, regardless of the ambient temperature. Figure 53 and Figure 54 show that the modelled results

allowed the temperature of the water in the collector to go below 0oC several times without any adverse

effects. During actual operation, water that is constantly freezing and thawing will put the collector and pipes


under stress and it is likely that they will break. This can be seen in the actual test results in Figure 49, where

the pipe in the collector broke after being put under stress from freezing.

The TRNSYS modelling only takes into consideration some types of frost protection that exist for a system.

Although only Model E5 claimed frost resistance, both Model E4 and Model E5 had a frost protection device

in the form of a circulation pump that switched on when water in the collector was 4°C or below and

remained circulating water until the temperature in the collector was 6°C (Model E4)/5°C (Model E5) or

higher. Not correctly modelling the heat loss that occurs when a pump circulated hot water from the storage

tank to the panels will overstate the energy savings that a system can offer.

Figure 53: Actual (top) and modelled (bottom) freeze test results for Model E4 (SF325)


Figure 54: Actual (top) and modelled (bottom) freeze test results for Model E5 (SE340)


AAE Solar Solahart

ABTT Solapac

AGP Solar Water Heating Systems

Apricus Solar Lord

AquaBlitz Solar Mio

Aquamax Solar Upgrade

ASSOSBOILERS Solar Wizard

AuscoSolar SolarArk

Austral Solar Company SolarElite

Azzuro Solar Solargain

BlueSky SolaRise

Bosch Solarland

Bright Generation Solarmax

Brivis Solarmaster

CEMA Solar Solaroz

Choose Solar SolarPeak

Chromagen SolarPower

Conergy SolarTech

Consol Solatra

Dux Solpure

ECCO Solar Steelfort

Ecosmart Stoddart

Ecosolar Stratco

Edson SUN RAY

Edwards Sun Surf

Endless Solar Sunflow

Everhot Sunheat

Greenglo Sunmaster

Greenland Systems Sunnon

Greenman Sunplus Solar

Heat Trap Sunray

Heavenly Solar Sunrise Solar

HELIOAKMI Sunseeker II

Hills Solar Sunshine Solar

Himin SUNSHOWER

Ice Solar Suntrap

Invert Energy Sunz

J V Solar Surface Power

JWsolar Switch

Kelvinator Thermann

Kingspan Renewables Thermastar

MEGASUN Thermasun

Micoe Thermocell

Modern Solar THERMOTEC

Natural Heat THSolar

Neopower TRIGEN

Nova Energy Solar Ultra Greensun

NOVASUN Urban Energy

Ozroll Velocity

Appendix 5: Solar water heater brands


Red-E-Heat VORMANN

Rheem Vulcan

Rinnai Westech Solar

Run On Sun Australia Wise Living

Sidek Solar Wizard

Skypower YES Solar

SKYSOLAR Your Energy Solutions Solar

Solaflair ZEN

ZEN Energy Table 18: List of SWH brands sold in Australia and New Zealand

Manufacturers and importers

Below is a list of questions which will help us understand the nature of the solar water heater market in

Australia and New Zealand. Your assistance in responding to these questions as well as any comments on the

state of the solar water heater market is appreciated.

• Are you a solar water heater manufacturer and/or supplier?

• Do you manufacture solar water heaters in Australia and/or New Zealand?

• Do you import any or all of your solar water heater components?

• Do you export your solar water heaters? If yes, approximately what share do you export?

• Do you know of any other Australian or New Zealand manufacturers that aren’t listed here?


The key issues raised in this product profile include:

1. Energy savings claims typically overstated compared to actual performance

2. Inability of consumers to select an appropriate water heater

3. Potentially poor SWH performance in cold climates (not captured in Standards)

4. Weak compliance with component-based and installation requirements

The product profile noted that possible options that could be used fall into four key categories:

1. No action

2. Improving Standards

o Improving the current energy savings modelling

o Cold climate specific issues

3. Information measures

o Mandatory climate-based energy efficiency labelling

o Public information campaigns and registers

4. Quality/minimum assurance measures

o Government compliance checking

o Other compliance checking

o Government backed minimum energy efficiency standards

Each of these options are discussed in turn.

No action

This potential option means that the status quo will continue. This will involve no new costs, benefits,

changes in productivity levels, emissions levels or changes in risk levels.

No action will mean that some SWHs will continue to be sold with components that either do not meet

standards or do not function as intended and poor levels of performance will be the result. Additionally

consumers (households and business) will continue to rely on energy savings claims when choosing a SWH

despite these claims generally overstating the level of performance a SWH may offer (when all components

work and the systems is correctly installed). This means that important purchasing decisions will be based on

only partially accurate information and there will be a degree of negative consumer feedback as a result of

expectations not being met.

Improving Standards

Improving the current energy savings modelling

Using a model to determine the efficiency and energy savings of a SWH can be quick and cheap. However,

the current TRNSYS model may not be providing results that accurately reflect real-life system performance.

Our modelling of SWH performance and energy savings has highlighted some shortcomings in the accuracy

of modelling when compared to actual test results. Improving the accuracy of the model through additional

inputs and compliance for key inputs would increase the complexity and cost of using the model and may

partially undermine the advantage of using a model instead of conducting full physical tests.

There are several possible methods of improving energy savings modelling and these are presented here,

although they each have benefits and drawbacks that need to be considered.

Improved inputs

The real-life testing of three electric boosted SWHs with no hot water demand showed that one of the SWHs

was boosting regularly despite the storage tank’s low levels of heat loss and generally good system

Appendix 6: Discussion of options


performance under standard test conditions. This boosting behaviour is likely caused or exacerbated by a

poor solar controller unit (the system’s computer). It is unlikely that this problem was apparent in the

manufacturer’s SWH modelling. Confirming how a solar controller operates with how it is assumed to

operate in the model may address this problem and improve the accuracy of modelled results more generally.

A research report available to the Department has also highlighted issues with the modelling of gas

consumption for gas boosted SWHs. This report presented results of in-situ SWH monitoring and showed

that modelled gas consumption was over-estimated for instantaneous gas systems and under-estimated for

storage (in-tank) gas systems. The calculated STCs for the monitored gas boosted systems gave results of

STCs for instantaneous gas boosted SWHs that were higher than the current modelled STCs. Calculated STCs

for the gas boosted storage systems were both higher and lower than the current modelled STCs. This

disconnect between modelled results and actual results is likely due to the model inputs from the underlying

AS4552 gas water heater standard.

While a model can be amended to include additional data inputs that help to quantify identified problems,

other problems may remain and some improvements to the model may not always be accurate or

appropriate. Rather than adding further complexity to the model and risking that additional issues remain

unidentified, a simpler way to ensure that a model provides reasonable results for a particular system may be

to conduct a physical test, to ground-truth the model for that particular system. If the modelled results were

similar to the physical test results, the model could then be ‘trusted’ to accurately estimate annual energy

consumption and the effect of different hot water loads and climates for that particular SWH system.

Checking a result with a physical test

A ‘ground-truthing’ physical test has recently been developed for heat pump water heaters. This was in

response to the E3 heat pump water heater product profile and RIS’s that found differences between

modelled energy savings claims and physical test results (similar to this product profile). This physical test

has been endorsed by industry and other stakeholders via Standards Australia processes.

The energy efficiency and climate dependent labelling requirements for all water heaters in the EU are

subject to a similar set of physical tests. This involves a 24-hour test with hot water drawn off in a

predetermined manner to replicate real-life conditions. For SWHs, components are tested separately (similar

to in Australia/New Zealand), with the load test occurring with no solar input. The results of the non-solar

load test are then combined with the results of the physical collector tests and measurements of pump and

controller energy use and used to model performance in multiple climate zones.

This approach to testing and modelling may be an option for Australia and New Zealand, to develop an

effective method of modelling. Alternatively, a number of small changes could be made to the AS/NZS 2712

stagnation test to either gather system heat loss information from existing tests to use directly in modelling

or to conduct a hot water draw-off test and use the resulting energy use measurements to double check the

accuracy of AS/NZS4234 modelled results.

Cold climate specific issues

There are some specific issues related to SWHs installed in cold climates and as most of the Australian and

New Zealand populations can be considered to live in cold climates, it is important for consumers to be aware

of these issues. The testing has raised three issues which affect many systems but affect those in cold climates

to a much greater magnitude. Based on the tests conducted to date it is not possible to fully quantify the

magnitude of some of these issues, however there may be a number of approaches that could improve

outcomes in these areas immediately.

Improving data on energy lost due to freeze protection and ‘clear sky’ (low irradiation) night

conditions

Systems that use circulation approaches for frost protection will lose energy through pump operation,

controller operation but most importantly by circulating hot water from the insulated storage tank to keep

the collectors from freezing. On a cold night the pump may operate many times. This issue will be far more

pronounced in winter where there is generally less solar energy in the day to heat the collector and longer,

colder nights where substantial energy may be lost from the collector.


This problem is not only applicable to split systems as during the freeze tests conducted as part of this

product profile all SWHs lost energy – including (non-pumped) thermosiphons and systems with used heat

transfer liquids such as glycol in the collectors. In each of these technologies the liquid in the collectors was

being cooled to low temperatures and this was cooling the water in the tank. Indeed, as a thermosiphon

storage tank is typically mounted immediately above its solar collectors, the cooled liquid in the collectors

may not need to ‘flow’ any real distance before it starts ‘taking’ energy from the storage tank.

In addition to the laboratory testing results, the Department is also aware of independent measurements and

observations based in and around Melbourne which helps to confirm such heat losses are occurring in real

conditions. A recent and comprehensive energy usage study in Melbourne found that solar systems were

using more energy than conventional systems in the colder months – so the level of solar gain during the day

must be less than the amount of ‘night time energy losses’ despite Melbourne having relatively mild winters

compared to other areas of Australia and much of New Zealand. In a second, individual situation the pump of

the open-circuit (water-based) split system was active most nights of the year, which often resulted in

significant amounts of energy being lost overnight. The relevant manufacturer would not replace or repair

the SWH (or pump) and the SWH owner was not able to convince consumer representative groups to

intervene. The first example shows that poor performance may be common in cold areas while the second

example shows that even if a consumer notices and measures a problem, they will need to pay to fix the

problem themselves or simply accept the high running costs.

While the energy savings modelling standard AS/NZS 4234 includes some adjustment for energy used by

open circuit pumped systems (systems that circulate water), such as pumping and heat loss, this adjustment

is not applied to thermosiphons or glycol systems. As all of the systems we tested lost heat energy and some

were also damaged during freeze testing (including a glycol based thermosiphon system), adjusting only for

the energy use of open circuit pumped systems does not appear reasonable. It is also not clear if the

magnitude of the adjustment in the standard is realistic, as it is not detailed.

The energy modelling Standard should be reviewed and amended to ensure that all such heat losses are

captured in an ‘energy savings’ claims in a realistic manner. This will help ensure that SWHs are only

installed where they can provide energy savings acceptable to the consumer. Additionally this will shift sales

of SWH in cold climates to SWH that are specifically designed to operate in such conditions and benefit the

manufacturers of these systems. Energy penalties should be applied to all systems affected by freezing

conditions, rather than only applying penalties to split systems that circulate water. The size of the penalties

may also need to be examined to ensure that the modelled penalties are similar to the actual energy impacts

of freezing conditions. Examination of the solar control may help inform how a split system may lose heat

through circulation and testing or research may be needed to quantify the effect of continuous ‘reverse

thermosiphon’ losses that can occur from a thermosiphon system in cold conditions. All water stored in a

solar collector at night should be assumed to cool.

Improving direct heat loss inputs

The second key cold climate issue raised by testing is that there are substantial heat loss differences between

the current standard heat loss test (based on storage tank heat loss at 20⁰C) and the heat loss that a SWH

installed in a cold climate will actually experience. This is an issue because energy savings modelling and

claims are based on tank-only heat loss at 20⁰C30, which results in energy savings claims that may be less

accurate, particularly for cold climate zones. The average temperatures for most of the Australian and

New Zealand populations are much lower than 20⁰C and many areas experience freezing conditions during

winter. In cold conditions, there is not only higher heat loss from the storage tank but plumbing fixtures,

collectors and pipes will also lose heat. E3 testing of tank-only heat loss at 20⁰C and system heat loss at 2⁰C

gave heat loss results that varied by up to 4.24 kWh or an increase of 137% (see page 37).

An option to address this issue may be to require more accurate modelling of system heat loss levels. It could

possible to measure the system heat loss at 20⁰C rather than just storage tank heat loss, or to conduct two or

more tests at different temperatures for either tank or system heat loss, so that heat loss levels at a range of

temperatures could be estimated. This option would create some additional costs, which would need to be

30 It should be noted that testing a storage tank at 20⁰C rather than a whole system in a range of temperatures makes the test simple and

relatively cheap, and can still provide useful heat loss information.


considered against the associated benefits. Cost could be minimised by using conducting just one test (at

20⁰C) and using the formulas in AS/NZS1056.4 which are designed to convert test results at 20⁰C to other

temperatures.

Another factor to consider with heat loss is the wind speed or air movement. Wind is important as higher air

flow leads to additional heat being lost from the storage tank. One manufacturer has raised concerns about

the accuracy of measuring the low wind speeds in the Standard so there may be a case for either increasing

the wind speed to provide more relevant results or to remove any wind requirements, simplifying testing, but

to impose a simple calculated adjustment to the heat loss result recorded in the nil-wind conditions.

System performance and durability

It is understood that as a result of these tests the relevant Standards Australia Committee is acting to

address some of the below issues. This action is to be commended. However for transparency, this topic is

still fully discussed below as it relevant to all SWHs installed to date and for SWH models already

approved for sale and still being manufactured.

The third key cold climate issue raised by testing is performance issues and system durability under freezing

conditions. Many areas of Australia and all of New Zealand experience frost conditions that could damage

collectors and pipes if the water inside them freezes and expands. To address this issue, AS/NZS 2712

requires that a ‘system designated as suitable for installation in frost-prone areas shall be effectively

prevented from suffering damage due to freezing’ and a defined test is presented as one way of

demonstrating this suitability. Collectors are currently required to be marked as either suitable for -5⁰C

conditions, -15⁰C conditions or not suitable for cold conditions without additional frost protection31.

SWHs are often installed with multiple collectors, especially in New Zealand and southern areas of Australia

that have lower solar irradiation levels and need more collectors to capture sufficient solar energy. However,

many manufacturers/importers appear to be testing just a single collector when conducting the solar

collector freeze test required by the Standard to determine a collector’s frost resistance. A larger number of

collectors will increase collector heat loss levels, which may increase the probability of freezing or damage in

the collectors or pipes if the SWH has insufficient frost protection.

During our freeze testing, all of the collectors that came with each SWH system were subject to freezing

conditions. All systems with flat plate collectors were tested with two collectors. The systems with evacuated

tubes were tested with 22 and 30 tubes respectively. Testing with the supplied number of collectors places a

more realistic strain on collectors, as well as the frost protection and circulation components of the SWH.

The requirements of freeze tests could be altered in order to ensure that the solar collectors used in cold

climates are sufficiently durable. Rather than subjecting a single collector to the freeze test, a test using

multiple collectors could be used to more accurately reflect real-life installations. To reduce the time and cost

of testing, multiple collectors could be tested for frost resistance and if they successfully passed, any number

of collectors equal to or lower than the number tested would be considered frost resistant for that system.

This is very similar to the current no-load system stagnation test in AS/NZS 2712 Appendix F. This test

allows a system to pass the requirements with any number of collectors that is equal to or less than the

number of collectors used in a successful stagnation test, as stagnation tests are more difficult to pass with a

larger number of collectors.

Of the three collectors declared as frost protected, one failed the freeze test in the final pressure test, one

passed but suffered a blockage due to freezing (so after more frost cycles it may have failed) and one passed

with no concerns. Additionally, one collector that did not claim frost protection but had a frost protection

valve passed the freeze test.

The system that claimed frost protection but failed the test used glycol as its heat transfer fluid. AS/NZS 2712

does not require a freeze test to be carried out for collectors that use a fluid that does not freeze until -15⁰C

conditions (or lower) are reached, such as glycol. The systems that experiences freezing in pipe work during

the test would also not be viewed as a failure under the Standard despite freezing damaging pipe work and

failure in pipe work being likely after multiple instance of freezing. So the exemptions and definitions about

31 See AS/NZS 2712:2007 4.10 for details


what constitutes a failure that underpin the freeze test in the Standard needs to be reviewed in light of these

results. This will help ensure that SWHs sold in cold areas are actually robust enough to not fail in such

conditions.

There are several real life examples of significant, large-scale SWH failures that have occurred in Australia

due to damage from frost to add weight to the freeze testing and associated recommendations. In 2010, there

was an instance of large numbers of SWHs in public housing properties in Sydney failing due to frost damage

during one cold weather period. There were also a large number of frost-related SWH failures that occurred

between 2008 and 2012 in Canberra. It was reported in the media that many SWHs of a specific brand that

were installed by a Canberra building company which failed during the winter months and in some cases

have failed up to three times - although it is not clear whether the systems or the installations were the cause

of the faults. Consumer forums such as Whirlpool and ProductReview also contain many discussions of

consumers whose SWHs have been damaged by frost conditions, as well as consumer confusion about what

frost protection methods exist and when frost protection is needed. While amending the freeze test may

increase the cost of testing for some systems, this cost needs to be weighed up against the substantial costs

that can and has occurred when SWHs fail – both in terms of damage to the SWH, possible damage to the

house (water leakage) and reputational damage to the SWH industry more broadly.

Information measures

Mandatory climate-based energy efficiency labelling

This policy option has been raised due to the perceived market failures affecting the ability of consumers to

make informed purchasing decisions. There is no consistent information on sizing, energy consumption

(running costs), climatic suitability or performance of SWHs. The inability to compare SWH performance or

suitability is compounded by the infrequent nature of water heater purchases, which means that consumers

find it difficult to select an alternative, more efficient water heater in a timely manner (GWA, 2009).

The main sources of information available to consumers, and their associated drawbacks, include:

• Manufacturer claims – These are varied in nature and often not comparable

• Information on energy savings– Energy savings relate to the potential amount of energy a SWH

could save compared to a conventional electric or 3 star gas storage water heater. The key inputs to

drive this potential are the amount of hot water usage (load) assumed by the modelling and the

climate it’s installed in. Most energy savings claims generally don’t state what the hot water load

assumption is, or provide a very broad ‘people per household’ figure (e.g. suits 1-3 people). This

makes information on potential energy savings of limited use, as a consumer will have difficulty in

assessing their hot water needs and how this relates to the potential energy savings. Concern about

the accuracy of the potential energy savings claims also have become apparent, through test and

modelling results

• Information on STCs (Australia) and ENERGY STAR® (New Zealand)

— In Australia, a SWH must be modelled to achieve 60% energy savings in climate zone 3 to receive

STCs for the specified load. Test and modelling results show that six of the eight electric boosted

SWHs tested achieved this requirement, as did all six of the gas boosted SWHs. However, when

modelled STCs were compared to claimed STCs, only three of eight electric boosted SWHs and three

of six gas boosted SWHs had similar STC claims32. While some differences may relate to the hot

water load sizes manufacturers used in their modelling, as such load sizes are not disclosed with the

STC claims – an additional issue for consumer transparency.

— For a SWH to be eligible for New Zealand’s ENERGY STAR label33, energy savings must be equal to

or greater than 70% in climate zone 5. The average level of energy savings claimed for eligible

ENERGY STAR systems is 75%, with claims of up to 87%. A claim of 87% energy savings means that

the system should use just 13% of the energy used by conventional water heater over the year, which

would mean that even in winter, when there is low solar irradiation, the SWH should substantially

outperform a well-insulated conventional water heater. However, while optimal installation and

32 Gas results need to be treated with caution, as tests weren’t performed with the collectors normally supplied with the systems. 33 http://www.energywise.govt.nz/node/9164

http://www.whirlpool.net.au/

http://www.productreview.com.au/

http://www.energywise.govt.nz/node/9164


operation of a SWH can provide 70% energy savings, a 2012 New Zealand parliamentary

commissioner’s report showed that energy savings for a typical SWH are 50-65% in New Zealand.

• Various industry and government information sources – These may be limited to

information about a specific brand (former) or provide very broad information (latter). The gas

industry currently labels residential gas water heaters, including those used in SWHs and provides

calculated annual energy consumption and star ratings.

Consumer labels

Introducing a mandatory climate-based energy label for SWHs could increase consumer knowledge and

understanding of SWHs, improve trust in available information and assist with purchasing decisions. Such a

label could present and standardise other important information that appears to be currently lacking in the

market, such as consistent sizing information. This information could also be supplied on the E3 Energy

Rating website to inform consumers seeking to conduct preliminary research for a water heater purchase.

These views, and the option to introduce an energy label, have received strong support across a range of

stakeholders in recent E3 consultations on heat pump and electric storage water heaters.

As the performance of SWHs is especially dependent on key climatic factors such as solar irradiance, ambient

temperature, and level and frequency of frost conditions, a consumer focused label designed to minimise

information failures would ideally carry climate-based information. Including climate-based performance

ratings would also help consumers in cold areas to select SWHs suitable for their climate.

The high recognition rate of energy labels on other appliances by consumers in Australia and New Zealand

would likely improve the impact of labelling SWHs.

A possible template for climate-based energy rating labels for Australia and New Zealand is currently being

designed with feedback from consumer and industry based focus groups. The final template will enable the

development of climate-based appliance labelling, which could be used for SWHs or all residential water

heaters.

The key features of a climate-based energy efficiency label tailored for SWHs could include:

• A star rating to compare that model’s energy efficiency in certain climates with other SWHs and

possibly with water heaters of other types

• A sizing metric to help consumers correctly size their SWH

• An indication of if the SWH is suitable for installation in a cold climate

• Estimated annual electricity/gas consumption

• A web-link (or QR code) that consumers can used to access additional information that cannot

reasonably fit on a label with the potential for information tailored to the location of the consumer.

There is a level of international precedence for water heater labelling. The European Union has recently

agreed to introduce energy efficiency labelling for all common water heating technologies. In the case of

SWHs, these labels will also include climate-based information. The proposed approach will provide

information on load (amount of hot water a system can provide), efficiency by climate zone, and expected

energy usage. The US passed legislation in December 2012 to develop a single energy efficiency rating for

water heaters. This will enable comparative labelling for both electric and gas based water heaters34.

However, SWHs are the only common hot water technology type not captured in the 2015 US water heating

energy efficiency minimum requirements35. Cross fuel labelling and harmonisation were identified as a

supporting measure for regulatory activities in the Australian National Hot Water Strategic Framework in

2008.

34 http://www.govtrack.us/congress/bills/112/hr6582/text 35 http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/27



http://www.govtrack.us/congress/bills/112/hr6582/text

http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/27


Figure 55: Proposed EU solar water heater label

While a label seems like an appropriate method to address information failures, there are important

underlying considerations of how testing and claims for such a label could work. The EU’s approach is based

on separate testing of SWH components. The overall system efficiency is then modelled against ‘average’,

‘warmer’ and ‘colder’ climate zones based on applicable European data inputs. This component-based

approach may be easy to adopt for Australia and New Zealand due to current local physical testing

requirements for energy efficiency also being component- based.

The current energy savings modelling used in Australia and New Zealand is also based on component

performance data. However, the testing and modelling results presented in this product profile have raised

concerns about the accuracy of the component-based modelling approach. To alleviate these concerns, an

alternative system-based test that uses current test requirements could be used to underpin the SWH label.

Public information campaigns and registers

The impact of some of the identified market barriers could be minimised through an information campaign

designed to educate both consumers and installers about the likely lifetime cost of SWHs, benefits of SWHs

and what to look for when buying a SWH. This could be conducted by industry or government.

There is some SWH information provided by New Zealand and Australian governments available to

consumers and installers. There was a SWH guide for consumers released by the Department of Industry in

2013 and distributed to organisations across Australia, but apart from this, there have been no targeted

public information campaigns by the Australian Government. In New Zealand, EECA provides SWH

information to consumers through its ENERGYWISE program.

In 2011, the Australian Government released plumber training materials with comprehensive information on

the installation and operation of SWHs. This was distributed around the country and training was provided

to interested parties in several states.


However, there is evidence that there is still a lack of information available to consumers and installers about

SWHs and that this lack of information is affecting optimal water heater choice and installation. Reports by

Miller and Buys and the Institute for Sustainable Futures have highlighted that there can be major

installation faults, such as incorrect collector orientation and incorrect pipe connections, which can result in

poor SWH performance. They also highlighted a lack of information available to consumers on how to

operate and maintain their SWH. Consumers are often unaware of optimal boosting methods, electricity

tariffs and maintenance requirements. The Institute for Sustainable Futures’ study ‘concluded that the lack of

information and maintenance was the major cause of the trouble people experienced with their systems’.

Public information campaign

Creating a public information campaign to inform consumers and installers of key suitability, installation,

operation and maintenance issues could address some of the many information barriers that exist. This

information campaign could be run through various approaches such as television advertisements,

newspaper advertisements, provision of SWH booklets to SWH retailers and installers, etc. However, given

that there are no pre-determined requirements for presenting information, it would still be difficult in the

current environment for consumers to compare like with like.

Public register

The creation of a public register that standardised the type and format of SWH information provided could

also assist in addressing information barriers. A form of standard information was raised by some E3

stakeholders who did not support an appliance-label based information approach.

Some manufacturers present information on various aspects such as SWH performance, energy efficiency,

durability and cost, but consumers may be more willing to accept these results if information was

standardised and displayed in a single location. Placing all current SWH information on a register would help

consumers to access useful, accurate information that is comprehensive and up-to-date. If compliance of

claims on the register was conducted, consumers could also be assured of the reliability of the information

provided. Studies have shown that in terms of SWH installations, it is important for consumers to access

basic, standardised information before their existing water heater fails, or be able to quickly access

information in the case of an emergency replacement (Wasi & Carson, 2011).

A requirement to provide such information could be either voluntary, which would lower cost but may risk

lower utilisation by manufacturers and consumers, or mandatory, which would be more expensive but also

more likely to be utilised and provide benefits. It could also be linked to eligibility for any future government

financial assistance. The requirement could be in the form of a product disclosure statement, similar to those

required for financial products such as superannuation and credit cards. A product disclosure statement

would provide all necessary information for consumers and would allow comparison between solar water

heater systems.

Product disclosure on the register could cover a range of factors, including:

• energy efficiency at selected operating conditions

• heat up time, hot water load or appropriate household size

• climate zone/s the SWH is suitable for

• suitability for cold climates and performance in cold temperatures

• ability to operate on an off-peak tariff

• other product characteristics that may be important to consumers

The difficulties and confusion that consumers face when making an important purchasing decision has also

been acknowledged in regards to solar PV systems. The Clean Energy Council has recently developed a Solar

PV Retailer Code of Conduct, which requires solar PV retailers to meet certain quality, sales, documentation

and business practice requirements. The code of conduct is a voluntary scheme that allows consumers to

make purchases with the confidence of purchasing a quality product, allows monitoring of solar PV retailers

and aims to improve customer service and industry standards.

The creation of a public register could also help with addressing the capital cost market barrier. It can be

difficult for consumers to understand and estimate the costs of purchasing a SWH, especially in relation to

the lifetime savings or payback period for SWHs. Providing reliable, comprehensive information on the


capital and running costs of SWHs will allow consumers to better understand the financial benefits of

installing a SWH.

It may be possible to provide a register of all financial options and assistance available to consumers who

purchase a SWH. There are many SWH manufacturers and retailers that offer finance options for consumers.

There are also some government programs in place to provide financial assistance. The register could include

information on options such as interest-free loans, system rental and monthly instalment payment plans, as

well as any available rebates or cash-back offers. This would assist consumers in identifying what financial

assistance is available and the reduced capital cost for a SWH purchase.

Quality/minimum assurance measures

Government compliance checking

While the SWH industry has benefited from a range of government incentives and regulations aimed at

encouraging consumers to install SWHs, SWHs are not subject to government energy efficiency regulation or

compliance checking of claims, especially physical performance testing. Most forms of government support

are based on the modelled energy savings that such systems can deliver, with formal test reports required to

provide evidence for design and construction matters including freeze and impact tests (AS/NZS 2712), tank

heat loss (AS/NZS 4692), collector efficiency (AS/NZS 2535), and gas heating efficiency (AS/NZS 4552).

Other model inputs include manufacturer-determined parameters, such as pump operation, control devices

and storage tank design features, and standard defined parameters, such as hot water demand and climate

assumptions.

TRNSYS modelling that was done based on the E3 test results showed that there were some significant

differences between manufacturer claimed energy savings for electric boosted SWHs and modelled energy

savings. Any over-claiming means that consumers may be misled, unjustified government support may be

provided and manufacturers/importers making accurate (lower) claims could lose sales share. An option that

could improve the accuracy of claims is the improvement compliance checks on such SWH claims. This could

require SWH components to be registered with government and therefore, a proper compliance regime could

be implemented, which would ensure that claims could be tested and unjustified claims could be subjected to

penalties and/or legal action.

Other compliance checking

While this document focuses on energy efficiency, the testing did find a range of other failures of SWHs to

meet Standards. These include failures to meet collect impact requirements, collector freeze test

requirements and gas consumption requirements. Additionally one system had a substantial fault in the solar

controller (see Figure 21, page 42) and one system did not properly heat its stored water - probably due to a

poorly located temperature sensor. These latter two issues do not appear to be directly covered by Standards

but will significantly affect ability of the SWH to function as intended.

Finding such a wide range of failures is disappointing and raises the observation that there appears to be an

unacceptably high rate of failures and faults. These faults are also in addition to the high level of installation

related faults already noted in this document.

While E3 policies typically focus on energy efficiency, they can also apply requirements relating to the impact

of that product on the environment or the health of human beings. In other cases, it may be better for other

government agencies or industry representative bodies to provide a basic level of consumer protection by

ensuring appliances are sufficiently suitable for their intended purpose. A relevant example of non-

government action is the Australian Clean Energy Council’s Accredited Installer program for solar PV

systems36. This program is designed to ensure consumers receive high quality, safe and reliable solar PV

systems.

As there appears to be a high level of problems, the cost of not introducing some form of quality control or

compliance checking will mean that consumers will be sold SWH that do not meet standards, do not operate

correctly and this will damage the reputation of both the relevant manufacturers but also the broader SWH

36 http://www.solaraccreditation.com.au/


industry. It is generally preferred that industry collaborates to ensure that Standards are being met and this

document challenges the SWH industry to suggest how such issues may be best managed.

Government backed minimum energy efficiency standards

Improving consumer information on SWHs may assist some consumers to make informed water heater

purchasing decisions, however there are other barriers to improving SWH performance and energy efficiency

that may need to be addressed separately. Barriers such as split incentives may justify the case for

implementing MEPS that ensure at least a minimum level of SWH performance.

Additionally, introducing MEPS will enable the government to conduct compliance testing on these

components to ensure that the component performance claims being made by manufacturers, importers and

retailers are correct. Compliance activities may also help to improve the quality of energy savings modelling

and claims, as component performance data is a key energy savings model input. As most of the Australian

and New Zealand SWH industries are already conducting component tests for STC eligibility (Australia) and

ENERGY STAR (New Zealand), the additional burden on the industry could be very low depending on how

the MEPS was set and how ‘strong’ the requirement would be. For example SWH manufacturers are all

claiming that they have very efficient storage tanks, so setting a MEPS at a level ‘worse’ that what is claimed

would mean that only manufacturers who are not making honest claims would be affected.

Solar collector energy efficiency

Of the eight solar collectors subjected to efficiency tests, there were no collectors that performed with poor

efficiency. As such, there appears to be little evidence of the need for a solar collector MEPS designed to

remove poor-performing collectors. Testing showed that selective coated flat plates and evacuated tubes are

both highly efficient, but have different efficiency ranges. Flat plates are more efficient at heating low

temperature water or in warm climates and evacuated tubes are more efficient at heating high temperature

water or in cold climates. While the flat plate collectors without selective coatings had lower efficiency levels,

such collectors may be cheaper and using a large area/number of these collectors may be more cost effective

than using smaller, but more efficient, collectors.

There does not appear to be much reason to remove low efficiency flat plates from the market. However,

implementation of a ‘weak’ solar collector MEPS would enable the government to conduct compliance testing

of collectors. This information could be used to help ensure that accurate collector efficiency data inputs are

being used in energy savings modelling, with the cooperation of the relevant Australian and New Zealand

bodies currently responsible for reviewing modelled savings.

Component heat loss

The key performance feature of a SWH is to capture energy from the sun and store it for future use. The

ability of a SWH to store hot water depends on the level of heat loss from the storage tank, tank fittings, pipes

and collector.

There are several sources of heat loss from a SWH that do not appear to be considered in energy savings

modelling. Component heat loss is affected by many external factors and addressing these sources of heat

loss could be done in different ways.

There are a few key points to keep in mind as it may not be practical to address or measure some types of

heat losses:

• Heat loss from various fittings will vary substantially depending on where they are located on the

tank. Many fittings are removed during tank heat loss testing, and resulting holes in the tank are

covered with insulation. Regulation of heat loss levels for these components would likely be complex,

especially if there was a trade-off with safety or durability. Examination of fitting heat loss does not

appear warranted.

• Tank heat loss for electric boosted systems is affected by what tariff the tank uses (off-peak systems

may be colder on average), while gas boosted systems are affected by the type of boosting (the water

in the storage tank that leads to an instantaneous boost may well be very cold). Tailoring heat loss

tests for different installations options does not appear warranted.


• Heat loss from collectors could be minimised however, any design and construction requirements

such as additional layers of glazing will likely reduce overall collector efficiency levels. Collector heat

loss in split systems may partially be largely driven by a SWH’s controller or pump settings and so

setting collector heat loss limits may not be the most appropriate way to address such losses.

The most significant heat loss component is the storage tank heat loss. SWH storage tanks are currently

excluded from the existing ESWH tank heat loss MEPS. Tank heat loss is a key data input for energy savings

modelling, however concerns about the levels of claimed heat loss used in modelling have been identified in a

separate E3 project examining electric storage water heaters. Claimed SWH heat loss levels tend to be better

than the minimum requirements set for ESWHs, but testing has shown that actual heat loss levels are

generally equal to or worse than the heat loss requirements.

The ESWH RIS examines the heat loss requirements for all electric storage tanks (conventional, solar or heat

pump water heaters) and proposes to simplify the regulatory arrangements for conventional ESWHs.

Stakeholder feedback was on heat loss arrangements was mixed with some advocating a checking of claims,

some advocating setting limits, some advocating the setting of overall system efficiency metrics and some

advocating that there should be no limits, checking or publishing of heat loss data.

System heat loss

An alternative option for examining SWH heat loss is to use system heat loss and create a system heat loss

MEPS.

Unless SWH system heat loss levels are measured or disclosed, there is little incentive for manufacturers or

installers to pay attention to collector and pipe heat loss apart from meeting minimum AS/NZS 3500.4 pipe

heat loss requirements. Requiring system heat loss to be measured and disclosed will provide consumers

with more accurate information about heat loss from their SWH and could be incorporated into energy

savings modelling.

System heat loss could be tested at 20oC, which would be cheap and consistent with how tank heat loss is

currently tested. Such a test is contained in AS 2984 but this Standard is now obsolete and no longer used –

this Standard is discussed in greater detail below.

Alternatively, testing at a range of temperatures could be done for the whole system, which would allow for

accurate calculations of system heat loss in each climate zone. This would be more expensive but would

provide more accurate heat loss and energy savings results. A simpler and cheaper alternatively may be to

have a single test, such as AS 2984, and the formulae in AS/NZS1056.4 could be used to adjust the 20oC

results to other temperatures.

System-based efficiency MEPS

The test results in this product profile have shown that there can be large variations between the results of

current component-based testing and real-life system performance. An example of this is Model E1, which

had good component-based test results, but relied on boosting in the real world testing, even when no hot

water was being used.

Another issue that exists is that there can be component performance issues that are not picked up in

component tests but are more likely to be picked up in system tests. For example, in our gas system testing,

Model G6 was not able to achieve the required tank water temperature, partly due to the thermostat being

too close to the gas burner (making the system respond as if all the stored water was hot when only some of

the water had been heated). This issue was not picked up in the tank heat loss test or delivery test, which

means that it was also not detected in the energy savings modelling. This is also complicated by the fact that

tank heat loss testing for gas boosted SWHs is done with an electric boosting element and not the supplied

gas booster (see AS/NZS4692.1).

These component issues have also been identified by the findings of a research report available to the

Department. The report monitored household solar water heaters and found that gas boosted storage SWHs

consume a much larger amount of gas than instantaneous gas boosted SWHs. However, when gas

consumption was modelled, the model over-estimated the gas consumption of instantaneous gas boosted

systems and under-estimated the gas consumption of storage (in-tank) gas boosted systems. This implies


either a problem in AS4552 (the gas water heater standard), AS/NZS4234 (the computer modelling

standard) or both and means that consumers wishing to purchase a gas-boosted SWH may be swayed by

modelled energy savings claims to buy a gas storage SWH when an instant gas SWH may have been a better

choice. These findings are supported by a conference presentation which showed that the amount of gas per

litre of hot water was vastly lower for gas instant systems that gas storage systems (Saman, 2013).

The current focus on component-based testing can result in difficulties for the consumer in identifying a

SWH with good system performance, as there is no assurance that a system with good component test results

will also have good system performance and efficiency.

There was previously a system-based test method for SWHs that was developed in response to requests by

the Australian solar industry and the CSIRO. This test is contained in AS 2984, however this standard is now

obsolete. AS 2984 involved hot water draw-off tests in both a no solar gain and a solar gain situation. These

tests were based on a variety of hot water loads, tariff restrictions and climate zones very similar to the

current energy savings modelling standard AS/NZS 4234. This obsolete standard helps to demonstrate that

concepts such as system heat loss and the need to ensure that an entire system performs well (as opposed to

just having good component performance) are not new concepts. The reintroduction of AS2984, to check that

AS/NZS 4234 test results are correctly simulating system performance, should be considered as a possible

solution to many of the testing and modelling issues outlined in this product profile.

It may alternatively be possible to introduce a system-based efficiency MEPS, by using a test method

approach similar to the previous AS 2984 test and the AS/NZS 5125 test recently developed for heat pump

water heaters and applying at the same time the AS/NZS 2712 stagnation test is conducted. The test in

AS/NZS 5125 involves drawing off hot water over a 24-hour period in a defined pattern based on

AS/NZS 4234 loads. It ensures that the system’s energy efficiency is tested in a manner consistent with how

its energy savings claims are calculated.

All SWHs in Australia and New Zealand are currently required to be tested to the AS/NZS 2712 stagnation

test. The stagnation test requires a SWH to be set up and subject to solar irradiation for several days to

ensure the system will not fail under conditions of high solar irradiation and no hot water demand. It would

be possible to add new aspects to this test, which would be relatively cheap, as the system would already be

set up for defined solar test conditions. For example, the test could be extended for 24 hours with the

collectors covered to gain a system heat loss figure. Alternatively, a series of water draw-offs could be

conducted while monitoring the system’s energy use. This would provide information on how different

components in the SWH work together and how much additional boosting energy is needed to meet the

required hot water draw offs.

It could also be possible to add a test to AS/NZS 2712 that requires SWHs to be tested under night

conditions, e.g. in cold temperatures with no solar radiation. This additional test could be run as a 24-hour

test, either indoors or outdoors, but performed in a similar manner to the AS/NZS 5125 tapping test. The test

could be run with colder ambient temperatures within specified temperature limits during the ‘night-time

hours’. This test would address performance issues and additional heat loss that SWHs in cold climates are

faced with, especially during night-time or winter when there can be no or little solar radiation. Again this

test could have substantial benefits for informing users in cold climates but would come at a cost.

Alternatively, the AS/NZS 5125 test could be modified to apply to SWHs by making small but important

changes, such as solar irradiance inputs and collector performance assumptions. If it is too complex or costly

to directly incorporate a solar collector sub-test into the AS/NZS 5125 test, an approach similar to what is

being introduced in Europe could be considered. The EU test will involve adding the results of the solar

collector tests separately to the system test results - this method is best described as a hybrid of a component

and system-based test.

As many combinations of solar collectors and storage tanks are currently able to be sold (provided each

component complies with the relevant standard), a full outdoor system test for each combination of

collectors and storage tanks would carry significant additional testing costs and time. However, it could be

possible to amend system test results for different sized collectors using simple calculations. This would help

to keep costs low while still providing quality information. Any draw-off test could also be used to ground-


truth or double check the results of component-based energy savings modelling and associated claims used

for rebate eligibility or building/plumbing code compliance.

In summary there are a number of possible ways in which a Government backed MEPS could be applied.

Each of the possible approaches has different levels of cost, benefit and complexity. Stakeholder comment

would be important for informing any such approaches.

We do not advocate any particular policy option, but rather aim to seek feedback from stakeholders on the

costs, benefits and opportunities associated with each of these options. We also welcome stakeholders to

propose any alternative options.

A joint initiative of Australian, State and Territory and New Zealand Governments

Product Profile: Solar Water Heaters

www.energyrating.gov.au

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