Comparing Load Profiles:Art or Science?

Roberta LaccettiNational Grid2005 AEIC Load Research ConferenceJuly 11, 2005

Question: Do class load shapes vary by…

State? Utility? Supplier? Transmission Congestion Zone? Year?

Answer: Yes. No. It depends on why you’re asking.

Real Questions: Can we use MA samples to represent NH rate

classes in COS filings?

Can we ignore one company’s samples after merger?

Do residential customer load shapes vary between utilities in MA?

Do we need to update our load shapes every year?

Approaches to Comparing Load Shapes

Traditional Load Research Statistics

Visual Comparisons of Graphs Normalized or Unitized All, Average, or Specific Days

Accounting for Errors in Estimated Loads

Some Statistical Summaries

Question #1: Can we use MA samples to represent NH rate classes?

Number of customers served in NH is less than 40,000.

Cost of Load Research relative to revenues is high.

MA is geographically close and good transfer methods can be used.

But… Regulators are unique Rate class definitions differ Appliance saturation varies

Average Residential Load Shapes: MA/NH

MA NH % Difference

Annual Use 7,912 kWh 8,034 kWh + 1.5%

CP Demand (4pm on Mon, 8/30/04)

1.54 kW

1.50 kW - 2.6%

12-CP Demand 1.44 kW 1.13 kW - 21.5%

Class Pk Demand

1.93 kW(7pm on Mon, 12/20/04)

2.07 kW(7pm on Sun, 1/25/04)

- 7.2%

Load Factor 46.5% 44.5% - 4.3%

Average Residential Load Shapes: MA/NH

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Average Residential Load Shapes: MA/NH

2004 Average Day

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Average Residential Load Shapes: MA/NH Peak Day with Error Bounds

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Monday August 30, 2004

Average Residential Load Shapes: MA/NH Some Summary Statistics Mean Bias Error:

-0.02

Root Mean Squared Error: .11

Coefficient of Variation of the Root Mean Squared Error: .13

Question #1: Can we use MA samples to represent NH rate classes?

Answer #1: No.

Ordered by the commission.

Question #2: Can we ignore one company’s samples after merger?

EUA/NEES merger resulted in rate consolidation.

Continuous and comprehensive samples existed in each company, doubling sample sizes.

Metering differences required two reading systems.

But… Regulators may want to evaluate impacts of

consolidated rates on customers, by company. Using one company’s samples to represent entire

territory may produce biased results.

Medium C&I Load Shapes: NEES vs. EUA Unitized Average Day - August 2001

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NEES EUA

Unitized Average Day Load Shapes: NEES/Combined

Percent Differences

Residential Small C&I Medium C&I

January -5.1% to 0.0% -2.3% to 0.7% -0.3% to 5.2%

April -6.2% to 0.1% -4.1% to 1.1% -0.4% to 5.9%

August -2.0% to 0.8% -3.0% to 0.5% -2.5% to 3.3%

Question #2: Can we ignore one company’s samples after merger?

Answer #2: No.

NEES-only samples would produce biased estimates of merged company classes.

Keep collecting data from both samples until new samples are implemented.

Convince Meter Services group that the quicker they install new samples, the sooner they can stop using old collection system.

Question #3: Do residential customer load shapes vary between utilities in MA?

Regulatory debate about Default Service pricing for customers with no competitive supply options.

We recommend a single price for utility-provided service in each load zone.

One Distribution Co. claimed differences in load profiles preclude a state-wide approach.

Comparison of Average Residential Load Shape:MA Utilities – Normalized 2002

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MECO NSTAR WMECO FGE

Question #3: Do residential customer load shapes vary between utilities in MA?

Answer #3: No. Supports company recommendations

on auction and pricing.

Question #4: Do we need to update our load shapes every year?

Cost-cutting in Operations area has been severe.

No regulatory requirement in NY. Wide range of practices in other companies. But…

Load shapes are used for commodity pricing

Load shapes support estimation of competitive supplier load and ICAP.

Comparison of 2003/2002 Load Shapes:Impacts on Pricing

Transfer methods considered:

Calendar Mapping

Day-Type Mapping

Weather Normalization

Comparison of 2003/2002 Load Shapes:Results Load estimation for pricing and settlement:

– Calendar mapping:– Load-weighted annual price = 1% below actual

– Weather model with 5 day-types and 4 seasons:– Load-weighted annual price = .01% below

actual

Peak hour estimate (ICAP):– Calendar mapping:

– Estimate of class demand = 1.9-29.7% below actual

– Prior year’s peak day (at peak hour):– Estimate of class demand = 6.1% below to

20.4% above actual

Question #4: Do we need to update our load shapes every year?

Answer #4: Maybe.

National Grid NE practices. Risk of criticism by market players. Timing of next rate case.

Summary

There are many different ways to compare class average load shapes.

Conclusions about similarities and differences should be based on how the shape will be used.

The answer may be, “It depends…”

Extra Credit Question:What is causing spikes in Residential Class precision levels?

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Clue

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November 2004