Comparing Load Profiles: Art or Science? Roberta Laccetti National Grid 2005 AEIC Load Research Conference July 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 % 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 MA= green, NH = blue

Average Residential Load Shapes: MA/NH

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

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

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

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): 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?

Clue