• If conditions worsen, utilities will determine how to rotate the outages.
  • The extreme heat that broiled the drought-ravaged state over the Labor Day weekend will continue for much of the week.
  • The vast area of high pressure sitting over the interior West is likely to weaken late this week.

Record-breaking temperatures were forecast to drive historic power demands in California on Tuesday, straining the electrical grid and making rotating outages increasingly likely, authorities said.

Over 500,000 customers in California were given advanced notice to prepare for potential rotating outages, often called rolling blackouts, by Tuesday afternoon, Pacific Gas and Electric said. Hours later, California’s electric grid operator issued Level 3 energy emergency alerts across the state, with imminent rolling blackouts “very possible,” the grid operator said.

Elliot Mainzer, CEO of the California Independent System Operator, said the “extraordinary heat event we are experiencing” makes it essential that homes and businesses reduce energy use after 4 p.m. That means not using major appliances and setting thermostats at 78 degrees or higher.

By 7 p.m. Tuesday, California’s grid reached peak demand at over 52,000 megawatts, hitting a new all-time record for the state. The state’s maximum capacity is 56,000 megawatts. Despite the troubling numbers, California’s grid operator noted on Twitter that “conservation is making a difference.”

The system declared an emergency Monday from 5 to 9 p.m. A “Flex Alert” urging consumers to reduce their power use in the late afternoon and evening remained in effect Tuesday, marking seven consecutive days the call to cut demand has been issued. 

“Over the last several days, we have seen a positive impact on lowering demand because of everyone’s help,” Mainzer said. “But now we need a reduction in energy use that is two or three times greater than what we’ve seen so far.”

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How would rotating outages work?

California’s grid operator issued a Level 3 energy emergency alert for residents in both Northern and Southern California on Tuesday, forecasting an energy deficiency across the grid and “imminent or in progress” blackouts.

Utilities will determine how to rotate the outages. The goal: keep them as short as possible. Mainzer said that for two days in August 2020, outages affecting about 800,000 homes and businesses lasted anywhere from 15 minutes to about 2½ hours – the first time outages were ordered in California because of insufficient supplies in nearly 20 years.

“We never want to get to that point, of course,” Mainzer said. “We want everyone to be prepared.”

WHAT YOU SHOULD KNOW ABOUT HEAT:From the heat index to a heat dome to an excessive heat warning

How California gets its power

California’s energy grid involves mostly solar and natural gas during the day, along with some imports of power from other states. But solar power begins to fall off late in the day, the hottest time in some parts of the state. Some of the aging natural gas plants California relies on for backup power struggle in hot weather.