What are rolling blackouts and will there be more of them?


A man sits on a bench in Berkeley’s Cesar Chavez Park while a huge plume of smoke rises up in distant Marin County as seen from Cesar Chavez Park. The smoke comes from one of several wildfires ablaze in the surrounding Bay Area. Aug. 19 2020. Photo: Pete Rosos

Over the past week, frightening weather patterns have disrupted our communities and strained public resources and utilities. The recent heatwave, expected to last the entire week, has seriously impacted the state’s electricity supply, leading many Berkeleyans to wonder if rolling blackouts are around the corner.

Berkeley didn’t experience power outages related to the heatwave or fires this week or last week, despite warnings from the city to expect them. But hundreds of thousands of residents lost power in other nearby counties over the weekend, and the blackouts reminded many of last year’s shut-offs, which began in the Bay Area and impacted 3 million people during an intense fire season.

Berkeleyside’s sister site, The Oaklandside looked into who manages and operates California’s power grid, how they responded to this week’s heatwaves and other unforeseen events, how much advance notice residents can expect about power shut-offs, and how to sign up for alerts and better prepare for rolling blackouts.

What are rolling blackouts, and why are Bay Area residents experiencing them?

The California Independent System Operator (CAISO), one of the largest grid operators in the world, manages about 80% of the state’s electrical grid. Based in Folsom, they’re the ones who order utility companies to shut off power and, when there’s enough time for advance warning, send out alerts to residents.

When CAISO anticipates strain on the state’s power grid because people are using too much energy relative to the overall supply, they tell utility companies to start conducting rotating power outages, commonly known as “rolling blackouts.” These outages are known as Stage 3 Emergencies, and you can find out about them by signing up for Flex Alert phone or email notifications. According to CAISO, these outages become necessary when the demand on the grid threatens to outpace the electrical reserves CAISO is required to maintain at all times by state law.

“This is not a transmission problem,” said CAISO vice president Mark Rothleder at a press briefing on Monday. “This is a supply, resource, and capability problem.”

CAISO determines whose power to cut off by grouping customers into rolling, or rotating, “blocks” and turning electricity off for targeted blocks for up to two hours at a time. You can look up your block using this tool from PG&E. If your block comes up as “50,” you’re unlikely to be affected by power outages because your address may be on the same circuit as a hospital, police station, fire station, or other critical facilities.

Andy Campbell, executive director of UC Berkeley’s Haas Energy Institute, said the rules governing the timing and locations of outages go back to the state’s 2000-2001 electricity crisis, when 1.5 million customers in California lost power in the state’s first blackout. That crisis — with 38 blackouts total — was exacerbated by a drought and the fact that three major utilities were dealing with severe financial problems at the time.

Several reasons lie behind recent power outages: hot temperatures leading to increased electricity demand, and unstable generation of wind power on Saturday due to heavy gusts.

CAISO also confirmed the temporary loss over the weekend of two power plants at Monday’s press briefing, but didn’t share many details. That loss in power also played into CAISO’s decision to rotate power shut-offs around the state.

Campbell acknowledged the hard decisions CAISO had to make this past weekend. “They have a tough job of keeping the system up and running,” he said. “The reason they black out some customers is so they can then keep power going to all the others. If supply and demand is out of whack, the whole system can collapse, and that could be very difficult to recover from.”

This weekend’s Bay Area power outages were not the same as PG&E’s Public Safety Power Shutoffs (PSPS), which are conducted in high fire-threat conditions to reduce the likelihood that a falling tree or faulty transmission line will cause a spark and fire. PG&E does not anticipate shut-offs this week, though there is always a chance it will happen later this fire season, which has started earlier than it did last year.

Along with heatwave-induced unplanned power outages like the ones we saw this weekend, fires can impact transmission lines and cause outages, too, though that fortunately hasn’t happened yet this summer.



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