California power disruptions are more likely if the heat wave gets worse.
As the state prepares to enter the most harsh stretch of the continuing heat wave, officials cautioned Sunday that the likelihood of power outages in California would increase over the next few days.
Mainzer warned reporters, "This is about to get substantially more intense."
But even as temperatures climb, Californians will still need to practise conservation to keep the lights on.
The majority of California's 39 million residents must endure stifling heat. Temperatures in the Central Valley are expected to be as high as 115 degrees Fahrenheit (46 degrees Celsius) for several days
In contrast, Los Angeles experienced exceptionally warm September temperatures, topping 100 degrees Fahrenheit (38 degrees Celsius).
Energy officials and power companies have been urging people since Wednesday to use less power from 4 p.m. to 9 p.m.
Keeping that number below 100 is our main objective, according to Mainzer.
About 5% of California's electricity supply on Sunday night came from nuclear power.