California heat wave: Gavin Newsom says rolling blackout risk is real. California’s power grid crisis became acute Tuesday with record demand projections.

California came to the brink of widespread rolling outages Tuesday evening as the grid operator said electricity supplies were running low amid unprecedented demand — but ultimately only a few Bay Area cities saw temporary outages.

Additionally, about 18,000 PG&E customers in the South Bay lost power through outages that were unrelated to the rolling blackouts, the utility said Tuesday night.

The Independent System Operator moved into Stage 3 emergency operations at around 5:30 p.m. Tuesday, allowing it to order utilities to initiate shutdowns if necessary as California’s record-breaking heat wave strained the grid, but it canceled that alert around 8 p.m. No rolling blackouts were ordered, said Anne Gonzales, a California ISO spokesperson.

California ISO issued another flex alert for 4 p.m. to 9 p.m. Wednesday, asking consumers to conserve electricity and help maintain power on the grid.

At least three Bay Area cities briefly turned off power in some areas Tuesday evening.

Palo Alto Utilities, the city’s municipal operator, said around 6:30 p.m. that power was shut off in response to the state efforts meant to reduce power demand. The agency said around 1,700 customers in the Midtown, Old Palo Alto and Industrial Park were affected by the outage. About half an hour later, the utility said power was restored after California ISO allowed it.

Alameda Municipal Power, the city’s public utility, said at 7:11 p.m. that power was shut off in the Marina Village and East End areas for an hour. A second hour of shutoffs was canceled and crews were working to restore power.

PG&E said Tuesday night it contacted 525,000 customers who might experience rotating outages lasting one to two hours.

At 6:39 p.m., the city of Healdsburg said it was directed by California ISO to turn off power for around one hour. At 8:10 p.m., the city said power outages were over due to lower system loads.

Separately, PG&E said that 18,125 customers were without power due to two seperate outages in the San Jose and Campbell area as of 9 p.m., said J.D. Guidi, a PG&E spokesperson. PG&E was not affected by rolling blackouts on Tuesday, he said.

One outage affecting 11,000 customers started at 3:02 p.m and there was no estimated time for restoration. The source of the outage was a downed wire on Fewtrell Drive in Campbell, and PG&E was investigating whether heat was the cause.

Another 7,125 customers in San Jose and Campbell were without power due to a failed transformer, in an incident that was likely heat related, said Guidi. There was no estimated time for restoration.

Officials pleaded with the public to reduce afternoon and evening energy consumption, a week into what is set to be the hottest and longest heat wave on record in the state for September.

California’s power grid escaped rolling blackouts through the long Labor Day weekend, but officials had escalated their warnings Tuesday, with the state’s electrical demand — primarily driven by air conditioning — setting a new record well before peak usage hours hit.

“We’re heading into the worst part of this heat wave, and the risk for outages is real and it’s immediate,” Gov. Gavin Newsom said in a Tuesday video statement.

Tuesday’s demand peaked at 52,061 megawatts — more than 3% higher than the 50,270-megawatt record set in 2006.

Wednesday’s peak demand is forecast to be 50,002 megawatts, the statement said, and the grid operator was already preparing for a possible declaration of emergency then.

For the seventh consecutive day, the grid operator has asked Californians to voluntarily conserve energy from 4 p.m. to 9 p.m. in requests known as Flex Alerts. Before 4 p.m., residents should pre-cool their homes. During peak hours, state officials ask Californians to avoid running major appliances, turn off all unnecessary lights and set the thermostat to 78 degrees or higher, health permitting.

To avoid outages, Californians need to conserve 2 to 3 times more energy than what was saved at the beginning of the heat wave, grid operator California ISO President and CEO Elliot Mainzer said Monday at a news conference.

Numerous power facilities were not operating at full capacity as of Tuesday morning, unplanned in nearly all cases, according to the grid operator’s daily power plant report. Heat can impede plants’ operations. During the heat wave, power plant operators have been asked not to take down their facilities for routine maintenance to maximize the power supply.

Early Tuesday afternoon, the state had already planned a Stage 2 emergency for the 4 p.m.-to-9 p.m. period. In a Stage 3 emergency, the grid operator asks utility companies to stand by before it orders rolling outages to lower energy demand.

Rolling outages are controlled, intermittent events designed to temporarily lower demand and prevent more devastating outages amid power supply shortfalls, said James Bushnell, a board member of the grid operator’s market surveillance committee and a UC Davis professor specializing in energy markets.

Numerous small-scale outages were also occurring across the Bay Area on Tuesday, probably for the most part owing to the challenges that power infrastructure such as transformers face in extreme heat.

Claire Hao and Roland Li are San Francisco Chronicle staff writers. Email: claire.hao@sfchronicle.com, roland.li@sfchronicle.com Twitter: @clairehao_ @rolandlisf

Claire Hao is A Hearst Reporting Fellow who joined the San Francisco Chronicle in 2022. She is a recent graduate of the University of Michigan, where she forayed into journalism at the student newspaper. Since then, she has interned on the news desks of Bloomberg Law and The Chicago Tribune as well as on the editorial board of The Washington Post. She was also the 2021 editor-in-chief of her college paper The Michigan Daily.

Having lived in Michigan for most of her life, Claire is really excited to begin her professional career by exploring two different cities. In her free time, Claire enjoys reading, writing, running and playing the guitar.

Roland Li covers commercial real estate for the business desk, focusing on the Bay Area office and retail sectors.

He was previously a reporter at San Francisco Business Times, where he won one award from the California News Publishers Association and three from the National Association of Real Estate Editors.

He is the author of "Good Luck Have Fun: The Rise of eSports," a 2016 book on the history of the competitive video game industry. Before moving to the Bay Area in 2015, he studied and worked in New York. He freelanced for the Wall Street Journal, the New York Times and other local publications. His hobbies include swimming and urban photography.