How California Avoided Rolling Blackouts in Historic Heat Wave

On Sept. 6, the power grid hit a peak demand of 52,061 megawatts—a new all-time record, according to state power authorities

Tropical Storm Kay broke up a record-breaking heatwave baking Southern California last week, but before the relief of rain, wind and cloud cover rolled past the coast, the triple-digit temperatures nearly broke the state’s overtaxed electric grid.

Fortunately, thanks to a series of critical decisions made by the California Independent System Operator on Sept. 6—a day when Sacramento reached a new heat record of 116 degrees—most citizens did not need to suffer through rotating power outages, which are implemented to reduce demand on the system and prevent larger scale “cascading blackouts.”

Elliot Mainzer, president and CEO of the California ISO, which manages the state’s power grid, said in a public update on the agency’s Youtube channel that Sept. 6 was an “extremely challenging day for California and the broader Western interconnection… We endured the hottest triple digit temperatures yet in a historic week-long heat wave.”

Mainzer added, “Demand for electricity peaked at 52,061 megawatts, a level we have not seen before in California.”

Despite a flex alert asking residents to reduce power usage the previous day, an effort culminating in 1,000 megawatts of scheduled savings, Cal ISO issued an Energy Emergency Alert 2, calling for emergency energy from all market resources and tapping into emergency response programs while encouraging consumers to conserve energy.

But by 5 PM, the statewide use of air conditioning in response to the heat began to take a serious toll, leading to an historic demand for electricity and a critical hour of decisions to maintain the power grid.

“The combination of customer demand reductions and other tools available to us under an Energy Emergency Alert 2 were insufficient, and at 5:17 PM, we triggered an EEA3 emergency,” Mainzer explained. “At that time, we notified utilities across our service territory to arm load in preparation for possible rotating outages.”

The situation continued to worsen, and by 5:45 PM, Gov. Gavin Newsom ordered the Office of Emergency Management Services to issue a rare state-wide emergency alert: “CAOES Conserve energy to protect public health and safety. Turn off nonessential power now.”


The messaging was successful, and Californians can pat themselves on the back for heading the warning and avoiding rolling blackouts.

“Over the course of the next half hour or so, we saw between 2000-2500 megawatts of load reduction which helped restore our operating reserves and ultimately enabled us to avoid a call for rotating averages,” Mainzer said. “That made an enormous difference in our efforts to keep the power flowing, and I can not thank the public enough for that response… If anything, last night showed us that we are facing very serious grid conditions that require a serious response.”

Mainzer added, “When we get a lot of people to change their behavior in just a few relatively small ways, we can accomplish big things.”

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