understanding electric
TRANSCRIPT
Understanding Electric
Bills + WAPA’s Net
Metering Program
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David Tucker
www.efcnetwork.org
Background: Energy and USVI
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US EIA Quick Facts: USVI
• USVI has few conventional energy resources and depends on
imported crude oil for electricity generation.
• As of January 2012, USVI electricity consumers were paying
an average price of $0.47/kWh.
• The Virgin Islands' largest solar project, the 451-kWh King
Airport photovoltaic array on St. Thomas, went into operation
in fall 2011 and provides 15% of the airport's electricity.
• Solar water heaters are required for all new construction.
• The huge Hovensa oil refinery on St. Croix has closed down.
• USVI is a pilot project of the Energy Development in Island
Nations (EDIN) program (cut fossil fuel use 60% by 2025).
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US EIA Quick Facts: USVI
Coal, Electricity, and Renewables (2009) • USVI does not produce coal and consumes only a small amount of that fuel.
• Electricity almost entirely by oil-fired generators using No. 6 heavy fuel oil & No. 2 diesel fuel.
• VIEO recently provided a grant for a 30-kW solar PV system to a local hospital in order to
help reduce govt. consumption of electricity from nonrenewable sources by 20% by 2012.
• The Energy Office also offers rebates for the installation of photovoltaic panels and solar
water heaters.
• USVI has potential for wind energy generation:
– Wind resources up to class 4 (up to 16.8 miles per hour at 50 meters above ground
level) are found at well-exposed sites along the central ridges of St. Thomas, St. Croix,
and St. John, as well as the northern, eastern, and southern coasts of the islands.
– The windward sides of the smaller islands also have wind energy potential with wind
resources up to class 3 (15.8 miles per hour at 50 meters above ground level).
– Wind speeds designated class 3 or higher are suitable for most utility-scale wind turbine
applications.
– In order to promote wind energy, the Virgin Islands Energy Office offers a 20% rebate
(up to $3,500) on the purchase price of wind turbines.
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Energy Management Goals
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Energy Management Goals
• Improve Energy Efficiency & Manage Total Energy Consumption
• Control Peak Demand for Energy
• Manage Energy Cost Volatility
• Improve Energy Reliability
These goals often overlap with other management practices (i.e. preventive maintenance program improves motor
efficiency and improves reliability)
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Improve Efficiency & Manage
Total Consumption • Cost of electricity is based on two main
components
– Quantity of electricity used (kilowatt-hours or
kWh)
– Demand for electricity
• On-peak vs. off-peak consumption affects
rates
• Understanding the electric utility’s pricing
policies (rate structures) is critically important
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Control Peak Demand for Energy
• Electric utilities typically include a “demand charge” in their rate structure – 30-60% of the overall cost of electricity
• Lower variability in electric demand over time (flattened demand curve) – Minimize changes in peak demand throughout the course of a
billing period
– Shifting loads from peak periods, typically during daylight hours, to off-peak periods
• Significant cost savings by minimizing demand charges – Indirectly – supplemental storage tanks
– Shifting loads to off-peak periods
– Minimize the overlap between treatment processes
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Manage Energy Cost Volatility
• Energy costs fluctuate much more
regularly than water costs
• Dramatic changes stress budgets
• Protect against volatility as much as
possible
– Long-term procurement of energy
– Provisions for alternative energy sources
– On-site generation of energy
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Improve Energy Reliability
• Water utilities should be able to provide
critical systems with adequate backup power
• Energy planning process should identify
opportunities to improve energy reliability
– Protection against complete loss
– Identify changes in power quality that can
damage equipment and/or
– Institute operating procedures to address
changes in overall power availability
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Electric Bills
I brought today copies of my own
electric bill.
A.True
B.False
True
False
50%50%
I already understand my electric bill
inside and out.
A.True
B.False
True
False
50%50%
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Share about your electric bills
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Understanding Electric Bills
• Now let’s look at a sample of a recent
commercial electric bill here in USVI from
the Water and Power Authority.
• You should also have a copy of this on the
table in front of you.
• Identifying information for the customer in
question has been blacked out.
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Sample Electric Bill
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Demand Charge (kW)
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Demand Charges
• Are measured in kilowatts (kW), a measurement of power demanded at a given instant in time.
• In this case, the customer is billed for 34 kW at a flat rate of $2.49/kW.
• There are no “demand ratchets” in this rate structure, where you can get “stuck” with paying for a peak of demand for a long while, such as an entire year.
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Energy Charge (kWh)
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Energy Charges
• Are measured in kilowatts (kWh), a
measurement of energy consumed across
the billing period (one month).
• In this case, the customer is billed for
16,571 kWh for a total of $1,473.76.
• Customer is billed in four blocks, as part of
a declining block rate structure.
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Energy Consumption Blocks
• Unlike a “uniform” rate structure, in a
“declining block” rate structure, you are
billed less per kWh when you pass certain
thresholds to the next block.
• So Block 2 is cheaper than Block 1, etc.
• This encourages higher consumption.
• An “increasing block” rate structure, by
contrast, encourages greater conservation.
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Customer Charge
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Customer Charge and
Miscellaneous Charges
• Standard in electric utilities everywhere,
there is a flat customer charge, not based
on consumption of kWh or demand for kW.
• Here it is $62.17 per month.
• There are also small Line Loss and Pilot
surcharges assessed by WAPA. They are
based on the number of kWh consumed.
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Fuel Charge
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The Big One: Fuel Charge
• The fuel charge, based upon the number
of kWh consumed, is by far the largest
component of this monthly electric bill.
• The fuel charge is $6,837.99.
• This covers the cost of fuel oil / diesel
which WAPA must import from off island.
• Without this charge, kWh rates would
merely be a reasonable 6-13 cents/kWh!
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Energy Measurements
• Electrical - Demand and consumption.
– Demand – kilowatts (kw) – think of as rated connected horsepower – how much horsepower for given speed, rate of flow?
– Consumption – kilowatt hours (kwh) – use of connected horsepower over time – how fast will it go and how long traveled at given speed?
• Energy benchmark – kwh/MPG how many miles per gallon at a given speed?
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Energy Measurements - kW & kWh
• Lights – watts or watts/1000 = kW
• Motors – horsepower x 0.746 = kW
• Direct Heat/Hot Water = kW
• Plug-Ins – computers, printers, heaters –
watts or watts/1000 = kW
• Quality Control Instruments = watts
• Btus/hr x 0.000293 = kW x 1 hr = 1 kWh
• 1000 watts: 1 kW x 1 hr = 1 kWh
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How Much Does It Cost?
Are you on the right rate schedule?
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Example: Billing Information Given: 1.5 MGD WT/WWT Plant
• Billing Demand – 250 kW, Contract Demand 350 kW
• Consumption – 130,000 kWh/month, 3Ø, PF > 0.85
Re-Sale Power - Rate Schedule
• Customer Charge - $ 50
• Demand Charge - $17.15/kW x (250-50)kW = $3,430
• Energy Charge – 15,000 kWh x 11.719¢/kWh +
(130,000 – 15,000) x 6.696¢/kWh = $9,458.25
• Month’s Electricity Cost - $12,938.25 + 2.83 % tax
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Demand Reduction Savings
• Most Significant Means
1. Operation Control and
2. Time of Use Contracting
Requires :
– Inventory of Large Motors
– Time of Use Operational Flexibility
– Knowledge of Utility Opportunity Windows
• Receive Double Dip Savings – Consumption and Demand Savings
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Time of Use (TOU) Contracting
• Electricity Cost Based Upon Reduced Rates for:
– Time of the Year
– Time of the Week
– Time of the Day
• Can Daily, Weekly, and Seasonal Operation be Controlled by Process Flexibility with Varying Throughputs? Storage Buffers Exist? Catch Up Capacity Good? Knowledge Indicators in Place?
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Windows of Opportunity - TOU
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Demand Shifting Example
• 300 kw with 50 kw Shifted to TOU Window
Service
Customer Charge $
Demand Kw $
Energy Kwh $
Total $/Month
SGS Utility B < 1000 Kw
$21 $4.89 x 300 kw
= $1,467
130,000 kwh x $0.0703/kwh =
$9,139
$10,606
SGS Utility B TOU
$21 $7.48/kw x 250 kw + 300 kw x
$1/kw = $2,170
On Peak 42,900 kwh x $0.0606 + Off Peak 87,100 kwh x $0.0485 =
$6,824
$9,034
Savings $1,572/Mo
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Effective Energy Management
• Conduct an Energy Survey
• Calculate the Demand and Consumption of the Largest Motors
• 100 Hp Motor May Cost $50,000/yr To Run Continuously
• Use Motor Master® if More Than 10 Large Motors – Free program download - US Dept. of Energy
– http://www1.eere.energy.gov/manufacturing/tech_assistance/software_motormaster.html
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Motor Master® Software 4.01
Repair vs. Replace Decision Basis
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Evaluating Pumping Efficiency
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Evaluating Pumping Efficiency
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Pump Size vs. Efficiency
• Impeller Sized for Best Efficiency
Point (BEP) Head & GPM?
• Are You in the Zone?
• Single 1,000 gpm Pump @ 400 ft. Head Cost $66,000 Annually At $0.07/kwh at 70% Pump Efficiency and $61,600 at 75% Efficiency
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Pumping – Best Efficiency Point
(BEP)
BEP
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Where You Operate Is Important!
Costly
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WAPA’s Net Metering program
• With the end of the USVI solar hot water
heater rebate program, WAPA’s net metering
program is one of the few incentives (in this
case, for solar PV) remaining here.
• Net metering allows you to sell back your
“excess” electricity from your solar panels,
beyond what you consume, to WAPA.
• Projections of what you will net meter back
can factor into your PV cost-benefit analysis.
Thank You
David R. Tucker
Project Director
Environmental Finance Center
School of Government, UNC-Chapel Hill
(919) 966-4199
http://efc.unc.edu