Weather Normalization

Presented by

John Avina

Abraxas Energy Consulting

1. Why2. How3. Reading Bills to Understand Building4. Humidity5. Benchmarking with Normalization

OUTLINE

Retail in Wisconsin

Retail in Wisconsin

• Average Weather….– Average of all the high and low temperatures

during the billing period

Retail in Wisconsin

Retail in Wisconsin

Retail in Wisconsin

Retail in Wisconsin

Retail in Wisconsin

Retail in Florida

Retail in Florida

Retail in Florida

Cooling Balance Point = 60

Retail in Florida

Cooling Balance Point = 67

Retail in Florida

Retail in Minnesota

Retail in Minnesota

College in Boston

College in Boston

Retail in San Francisco

Recap: Why Use Weather?

International Performance Measurement and Verification Protocol

•

M and V Standards

www.ipmvp.org

Federal Energy Management Guidelines•

M and V Standards

http://www.eere.energy.gov/femp/pdfs/26265_seci.pdf

ASHRAE Guideline 14•

M and V Standards

http://www.ashrae.org

IPMVP M&V Options4 Methods of M & V4 Methods of M & V

•Option A - Partially Measured Retrofit IsolationOption A - Partially Measured Retrofit Isolation

•Option B - Retrofit IsolationOption B - Retrofit Isolation

•Option C - Whole (or Part) Building (Utility Bills)Option C - Whole (or Part) Building (Utility Bills)

•Option D – Calibrated SimulationOption D – Calibrated Simulation

Methods chosen based upon budget, need for accuracy, ECMs installed, Methods chosen based upon budget, need for accuracy, ECMs installed, Metering SetupMetering Setup

• Option A - Partially Measured Retrofit IsolationOption A - Partially Measured Retrofit Isolation– Partial short-term/continuous measurements – Partial short-term/continuous measurements –

some but not all stipulatedsome but not all stipulated– For Separable ECM Savings Determination - For Separable ECM Savings Determination -

Lighting Lighting

IPMVP M&V Options

• Option B - Retrofit IsolationOption B - Retrofit Isolation– Full short-term or continuous field measurement - Full short-term or continuous field measurement -

no stipulationsno stipulations– For Separable ECM Savings Determination - HVAC For Separable ECM Savings Determination - HVAC

subsystemsubsystem

IPMVP M&V Options

IPMVP M&V Options

• Option C - Whole (or Part) BuildingOption C - Whole (or Part) Building– Full continuous energy use and demand Full continuous energy use and demand

measurement during Baseline and Post- Retrofit measurement during Baseline and Post- Retrofit Periods Periods

– Collective Savings of all ECMs for Area monitored by Collective Savings of all ECMs for Area monitored by a Single Metera Single Meter

IPMVP M&V Options

• Option D – Calibrated SimulationOption D – Calibrated Simulation– Computer-based simulation of energy use of Computer-based simulation of energy use of

building componentsbuilding components– Simulation Calibration, Considerable skills, Simulation Calibration, Considerable skills,

Costly ???? Costly ????

Suppose an ESCO chooses Option C, Utility Bill Analysis...

Why would an ESCO want to correct for weather

Why Not keep it simple and just compare pre and post retrofit bills

Billions of Dollars of savings are tracked using Option C

M&V and Utility Bill Analysis

0

50,000

100,000

150,000

200,000

250,000

June 2004 June 2005

kWh

Suppose an ESCO expected this from a Chiller Retrofit….

Savings

Why Utility Bills Don’t Why Utility Bills Don’t Always Yield Savings?Always Yield Savings?

…and instead got this….

0

50,000

100,000

150,000

200,000

250,000

June 2004 June 2005

kWh

Increase

Why Utility Bills Don’t Why Utility Bills Don’t Always Yield Savings?Always Yield Savings?

Why Aren’t There Any Savings?

What Do We Tell the Customer?

Will I Keep My Job?

Will I Get My Bonus?

Seen Him Before?Seen Him Before?

How Can They Show Savings This Year?

The ESCOs’ Dilemma

How Can They Show Savings This Year?

The ESCOs’ Dilemma

Real Data

Cooling kWh ~ CDD

Which means…

double CDD

double Cooling kWh

Retail in Minnesota

How to Perform Weather Normalization

Start with Bills and Weather Data

Determine How Bills Vary with Weather

Electric used to Heat & CoolElectric used to Cool Only

Using Weather toUnderstand Bills

Balance PointNon-Temperature Sensitive Usage

Cooling Balance Point is the Temperature at which the Building Starts to Cool.

Low Cooling Balance Points indicate Outside Air is NOT being used for Free Cooling.

Temperature Sensitive Usage

Estimate Balance Point

Balance Point

Non-Temperature Sensitive Usage

Temperature Sensitive Usage

Balance Point is the Temperature at which the Building Starts to Heat.

Estimate Balance Point

1. For each day in Billing period…

CDDi=(Ave Outside Temp - Bal Point Temp) X 1day +

Where Ave Outside Temp is the average between high and low temperature for the day.

And Bal Point Temp (balance point temperature) is the balance point found in the previous slide.

You cannot have negative CDDs

2. CDDBilling Period = (CDDi)

Calculate Cooling Degree Days

1. For each day in Billing period…

HDDi=(Bal Point Temp - Ave Outside Temp) X 1day +

Where Ave Outside Temp is the average between high and low temperature for the day.

And Bal Point Temp (balance point temperature) is the balance point found in the previous slide.

You cannot have negative HDDs

2. HDDBilling Period = (HDDi)

Calculate Heating Degree Days

Perform a Linear Regression between Energy Usage and CDD (and/or) HDD. Find the best fit line.

This is the Cooling Balance Point.

Cooling Balance Point is the temperature at which the building starts cooling.

Weather Normalization

Normalization Tools

You can use Excel or Canned Software

There are Several Desktop applications that handle weather Normalization, one of which specializes in it.

Your Fit Line Has an Equation, which is called the Baseline Equation

y = mx + b

which could be rephrased into something like this

kWh = 61.986 x #CDD + 1872.7 x # days

Understanding the Baseline

Energy Balance

Use the Regression Coefficients to True Up Energy Balance

Your Fit Line Has an Equation, which is called the Baseline Equation

Baseline Equation = Best Fit Line ~ Base Year Bills

So now we can work with the Baseline Equation and throw out the bills. We don’t need them any more.

Baseline Equation represents your energy usage patterns during your Base Year

Understanding the Baseline

What Good is the Equation?

We take a Current Year Bill,

determine # of days in the bill,

determine # of CDD (or HDD)

and plug those into the Baseline Equation.

Baseline kWh = 61.986 x #CDD + 2872.7 x # days7/21/05 Bill

100,000 kWh

700 CDD

30 days

Baseline kWh = (61.986 x 700) + (2872.7 x 30)

Baseline kWh = 129,571 kWh

Understanding the Baseline

What Good is the Equation?

So Baseline kWh represents how much energy your facility would have used this year given current weather conditions and Base Year usage patterns.

The Baseline Equation represents Base Year Usage patterns, and we applied Current Year weather to it

Baseline kWh = 61.986 x #CDD + 2872.7 x # days7/21/05 Bill

100,000 kWh

700 CDD

30 days

Baseline kWh = (61.986 x 700) + (2872.7 x 30)

Baseline kWh = 129,571 kWh

Understanding the Baseline

Understanding the Baseline

What Good is the Equation?

Savings is Baseline Usage – the Actual Bill Usage

Baseline kWh = 61.986 x #CDD + 2872.7 x # days

7/21/05 Bill

100,000 kWh

700 CDD

30 days

Baseline kWh = (61.986 x 700) + (2872.7 x 30)

Baseline kWh = 129,571 kWh

Savings = Baseline kWh - Actual kWh

Savings = 129,571 kWh – 100,000 kWh

Savings = 29,571 kWh

Savings then…Savings = Baseline – Actual

Which is …

how much we would have used – how much we did use

Wait a Second!

You don’t have to do all this math!

Wait a Second!

Starts cooling at 46 degrees?

Runs on a working control system

Very large non-temperature sensitive usage

non-temperature sensitive usage

temperature sensitive usage

Reading Bills

Correlation to HDD

Much Noise…poor control operation or don’t understand the meter

Starts heating at 65 F degrees

Reading Bills

More…

You Can Normalize with More than Just Weather.

•Normalize to:

•Production,

•School Calendar,

•Occupancy

•Or Something else

Normalizing with Humidity

LOAD FACTOR

0%

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80%90%

100%

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LF %

BEACH HS

GROVES HS

JENKINS HS

SAVANNAH ART ACAD

SAVANNAH HS

WINDSOR FOREST HS

Average

dayhrs

NkW

kWhkW

kWLF

daysmtrmtr

ave

24

Load Factor is a measure of demand relative to usage.

It can indicate how the building is using energy.

dayhrs

NkW

kWhkW

kWLF

daysmtrmtr

ave

24

dayhrs

N

kWhkW

days

ave

24

LOAD FACTOR

• LF = 1 implies uniform levels of use (no high peak demand)

• LF ~ 0.2 implies very high peak demands

kW

Hour of the Day

LF gives an idea where energy manager should focus.

If LF is high (above .7), focus on reducing usage, not demand.

LOAD FACTOR

Billing error? Change in

Usage Pattern

Why is the purple line the highest?

LOAD FACTOR