4 May 2004 – Heavy air conditioning use amid triple-digit temperatures triggered a transmission emergency in California on Monday and some businesses were asked to turn off the lights.
The California Independent System Operator said it had asked utility Southern California Edison to call upon business customers in its voluntary interruptible program to shut down.
These customers receive power at a discount in return for agreeing to shut down when supplies become very tight.
SCE, based in the Los Angeles suburb of Rosemead, can save around 600 MW through the programme, roughly enough electricity for 500 000 homes.
ISO spokeswoman Stephanie McCorkle said demand in its control area had exceeded 40 GW for the first time this year on Monday afternoon. The grid operator said it did not anticipate seeking rolling blackouts.
SCE is a unit of Edison International.