The California Independent System Operator has extended the Flex Alert across the state for the 10th straight day.
All Californians are asked to cut their energy use from 4 p.m. to 9 p.m.
The alerts come as the heatwave lingers on, putting a strain on the state's power grid. Officials say energy shortages are expected.
State officials urged the public to pre-cool their homes to 72 degrees and use major appliances before 4 p.m. to minimize discomfort and help with power grid stability.
A Flex Alert is issued when the electricity grid is under stress due to generation or transmission outages, or from persistent hot temperatures.