The California Independent System Operator, which runs the state's power grid, is bracing for energy deficits and said rotating outages are possible on Monday.
Elliot Mainzer, chief executive officer of the system, said, "We have now entered the most intense phase of this heat wave . Forecasted demand for Monday and Tuesday is at all-time record levels and the potential for rotating outages has increased significantly."
The state is looking at energy deficits of 2,000-4,000 megawatts-- up to 10 percent of normal electricity demand.
Mainzer added that the state needed two to three times as much conservation to avoid power outages.
During historic heat across the state over the past five days, consumers have done better than expected, officials said.
Power use over the past two evenings came in about 1,000 megawatts below what was expected -- about two percent below the state's forecast for energy use, Mainzer said.