(Reuters) - As homes and businesses crank up air conditioners to escape a lingering heat wave, California's power grid operator again urged customers to reduce their energy use for just one more day to avoid stressing the electric system.
Demand for power reached 46,847 megawatts (MW) on Monday, the highest so far in 2012, and was expected to break that record again on Tuesday, the state's grid operator, the California ISO, said Tuesday.
The ISO forecast that demand on Tuesday would reach 47,497 MW. That is still well below the grid's all-time peak of 50,270 MW set in July 2006 before the Great Recession cut mostly industrial and commercial demand for power.
The ISO said conserving power was especially important this summer because the giant 2,150-MW San Onofre nuclear power plant remained off line. The two reactors at San Onofre were shut in January due to problems with tubes in the units' steam generators, which heat water into the steam that turns the turbines to generate electricity.
Southern California Edison (SCE), a unit of California power company Edison International and San Onofre's operator, has not yet said when the reactors might return to service.
The plant's owners include SCE and San Diego Gas & Electric, a unit of California power company Sempra Energy.
The ISO said consumers could reduce their energy usage by 1,000 MW or more, which is enough to power a million homes.
In its so-called Flex Alerts, the ISO recommends that customers turn off all unnecessary lights, postpone using appliances until after 6 p.m. local time and turn air conditioner thermostats up to 78 degrees Fahrenheit (26 Celsius).
During this heat wave, the ISO started issuing Flex Alerts on August 9.
High temperatures in Los Angeles, the second biggest metropolitan area in the United States behind New York, were expected to reach 88 degrees F on Tuesday, but the humidity will make it feel more like 98 degrees, according to weather forecaster AccuWeather.com.
Temperatures in the City of Angels have topped 90 F for three days in a row on Saturday, Sunday and Monday, but were expected to return to near normal in the mid 80s on Wednesday.
In addition, to the flex alerts, the ISO restricted maintenance operations for the state's generating companies and transmission owners, including units of PG&E Corp, Edison International, Sempra, GenOn Energy Inc, Dynegy Inc, AES Corp, NRG Energy Inc and Calpine Corp.
(Reporting By Scott DiSavino in New York; editing by Andre Grenon)