https://www.siliconvalley.com/2021/06/26/opinion-californians-electricity-conservation-needed-this-summer/

As California transitions to much greater use of renewable energy resources like solar and wind power, and new battery technology to store that power, the state’s electricity grid remains vulnerable to widespread heatwaves like the one that hit much of the Western United States last summer.

That’s because when it gets really hot across the West, there is less power to import into California, especially during the period from 4 p.m. to 9 p.m. as solar energy production declines while the demand for power remains high.