2011 Load Impact Evaluation of California's Statewide Base Interruptible Program

This report provides the 2011 ex post load impact estimates and 2012-2022 ex ante load impact estimates for the Base Interruptible Program (BIP), which is offered by each of California’s three major investor-owned utilities, Southern California Edison (SCE), Pacific Gas and Electric (PG&E) and San Diego Gas & Electric (SDG&E). In addition, the report provides an overview of the program and detailed discussion of the evaluation methodology.

Each utility called a territory-wide test BIP event in 2011. SCE called a test event on September 21 from 2 PM to 4 PM, which provided an average load drop per customer of 790 kW and an aggregate impact of 522 MW. This represents nearly a 70% reduction relative to the estimated reference load of 751 MW. PG&E implemented a test event on September 7 from 3 PM to 5 PM, which provided an average load drop per customer of 827.5 kW and an aggregate impact of 183.7 MW. This represents roughly an 83% reduction relative to the reference load of 220.9 MW. SDG&E called a BIP test event on August 18 that lasted from 12 PM to 4 PM for BIP option A customers and 3 PM to 6 PM for the single BIP option B customer. From 3 PM to 4 PM when all SDG&E BIP customers were participating in the event, the average load drop per customer was 114.1 kW and the aggregate impact was 2.4 MW. This represents roughly a 35% reduction relative to the reference load of 6.9 MW.

In addition, BIP ex ante load impact estimates were developed for the years 2012 through 2022. These estimates show that BIP is a large, statewide emergency resource that is expected to experience modest growth over the next few years. For the August monthly peak day in a 1-in-2 weather year, the program is projected to deliver 778 MW in 2012. By 2018, the aggregate load impact is expected to grow by 10.2% to 854 MW. This growth is a result of increased enrollment among PG&E and SDG&E BIP customers and load growth among SCE and PG&E participants. From 2018 through 2022, the aggregate impact decreases slightly because PG&E anticipates a small decline in BIP enrollment and in usage among its large business customers in those years. In each forecast year, around 72% to 76% of the aggregate load reduction comes from SCE, 24% to 28% from PG&E and the remaining 0.2% to 0.7% from SDG&E.

Read the Full Report