California grid operator calls for power rationing as state sizzles

California's grid operator is calling for people to limit their electricity usage amid a historic heat wave that is straining the power system in the U.S.' most populous state. 

The California Independent System Operator (CAISO), which oversees the state's power grid, on Tuesday afternoon issued an "emergency alert" asking residents to use less power between 4 p.m. and 9 p.m. 

"[R]eal-time analysis shows all resources are committed or forecasted to be in use, and energy deficiencies are expected," CAISO said in a bulletin. 

The grid operator expects power demand on Tuesday to rise to 52,000 megawatts, exceeding records set in 2006. 

California and other parts of the West face a brutal heat wave, leading to increased power consumption as people try to keep cool. Temperatures in California's Central Valley are expected to be as high as 115 degrees Fahrenheit for several days, while in Los Angeles temperatures topped 100 degrees, unusually hot for September. 

CAISO expects a majority of weather stations in California's interior to break daily temperature records on Tuesday. In neighboring Oregon, meanwhile, at least 12 cities broke temperature records for July and August, Oregon Public Broadcasting reported.

Heat strains the electricity grid by increasing demand for air conditioning, and it also makes power transmission less efficient and more prone to failures. The heat on Tuesday knocked out power for more than 2,500 residents in the East Bay community of Livermore, CBS San Francisco reported.

At the same time, this summer's intense drought has dried up reservoirs, cutting into normally reliable hydroelectric power.

"We're heading into the worst part of this heat wave, and the risk of outages is real, and it's immediate," Gov. Gavin Newsom said on Twitter.  

Officials are urging Californians to run their air conditioning earlier in the day, when more power is available, and to turn up the thermostat starting at 4 p.m. They're also asking people not to use large appliances, like washing machines, dishwashers and dryers, between 4 p.m. and 9 p.m., which are peak hours for electricity use.

Scientists say climate change has made the West warmer and drier over the last three decades and will continue to make weather more extreme. The North American Electric Reliability Corporation, which oversees the nation's electricity grid, has warned that more extreme weather and its strain on infrastructure is likely to lead to more frequent blackouts, particularly in the West and Midwest. 

Several hundred thousand Californians lost power in rolling blackouts in August 2020, although the state fared better last summer. 

Last week, Newsom signed legislation potentially allowing the state's last remaining nuclear plant to stay open beyond its planned 2025 closure in order to ensure more power for the energy grid.

The Associated Press contributed reporting.