According to the U.S. government’s Energy Information Agency, California actually has installed electricity generation capacity of almost 76 GW. That sounds like wildly more than you would ever need. But the problem is that of the 76 GW of capacity, some 27 GW is solar, and 6 GW is wind. In August the solar goes into steep decline around 4 PM and ends completely around 7 PM. The wind more or less doesn’t blow at all during heat waves. And thus you get a profile of electricity generation from the renewable sources that looks like this (this is the report of generation from renewables in California for August 14, 2020, per CAISO):
