The Washington PostDemocracy Dies in Darkness

How extreme heat is straining California’s electrical grid

A worker fixes a street lamp in the Van Nuys section of Los Angeles on June 17. (Richard Vogel/AP)
Placeholder while article actions load

Less than a year after a severe heat wave triggered rolling blackouts in California, soaring temperatures are once again straining the state’s electrical system.

California’s grid operator on Thursday called on residents to reduce their energy use as triple-digit heat seared the central and southwestern parts of the state and its neighbors, breaking temperature records in some places. The “flex alert” is the first issued by the California Independent System Operator so far in 2021 and comes days before the official start of summer.

Officials and experts said the grid is better equipped now to handle a hot-weather surge in electricity demand than it was last August, when residents endured rotating power outages because of the heat for the first time since 2001. But California’s system still could face electricity shortfalls if the region is scorched again this summer.

Why is California asking people to cut back on electricity usage?

The California ISO’s “flex alert” asks residents to voluntarily cut back on their electricity use between 5 p.m. and 10 p.m., when demand peaks.

During those hours, people come home from work or school, fire up their air conditioners and switch on appliances, increasing the load on the grid. As the sun sets, electricity flowing from solar energy sources diminishes, meaning there’s less power to go around. At the same time, temperatures outside remain high well into the evening and structures retain the heat they’ve absorbed during the day, pushing air-conditioning loads even higher.

Conserving energy at those key times reduces the stress on the grid that can lead to blackouts.

“It’s the first stage of saying, ‘We might have a problem, so please don’t use electricity without considering what you’re doing,’ ” said Jim Williams, an expert in energy systems at the University of San Francisco. “You’re relying on the goodwill of the people to chip in.”

Thursday’s “flex alert” calls on Californians to set their thermostats to 78 degrees or higher during the evening and to use fans instead of air conditioning when possible. It also asks residents to close their drapes, turn off second refrigerators and defer tasks such as vacuuming, laundry and dishwashing until later in the night.

“Tens of thousands of households modestly adjusting their consumption can have a big aggregate impact,” Williams said.

How likely are rolling blackouts?

Last summer, the California ISO ordered rolling blackouts after electricity reserves dropped below a critical threshold during the August heat wave that baked the western United States. Hundreds of thousands of customers were affected by the outages, which lasted about an hour at a time.

California ISO President Elliot Mainzer said this week that another round of outages was unlikely in this case but urged residents to rein in their electricity use.

“Californians have stepped up many times before when asked to pitch in,” Mainzer said in a call with reporters, “and I’m confident they will do so.”

Experts agreed that the state would probably avoid forced blackouts this time.

States in the West share power with one another, with California in particular importing a significant amount of its electricity from Arizona, Nevada and the Pacific Northwest. Last summer’s heat wave fell hard across several states simultaneously, driving up demand throughout the region and leaving less power for California to import. One of the few mercies of the current wave is that it isn’t quite as widespread, according to Williams.

“This has been a vast heat wave, but the intensity has varied across the West,” Williams said. “When everybody goes through a heat wave, nobody has anything to share. Last August was a wake-up call that you can’t always rely on the West having excess energy flowing around.”

Is the grid better prepared than it was last year?

After last summer’s outages, officials took a number of steps to prevent a repeat. They delayed the decommissioning of some gas-fired power plants to squeeze out more generation. Utilities started installing more batteries for backup during peak load in the evenings when solar generation wanes. Officials also have proposed changes to market rules to prevent electricity exports when demand is high.

“More blackouts are not an inevitability,” said Steven Weissman, an energy law expert and lecturer at Goldman School of Public Policy at the University of California at Berkeley. “There were improvements made. The question is: Were those improvements enough? It’s very difficult to predict the answer to that question.”

In a report in May, California ISO officials said they expected energy supply conditions to be better in 2021 than they were last year but cautioned that they continued “to see potential challenges in meeting demand during extreme heat waves.” The report said the operator remained “guardedly optimistic regarding its operations this summer given the measures already taken.”

How could this year’s drought affect the availability of power?

California’s deepening drought leaves the state vulnerable to grid disruptions.

The state relies heavily on hydroelectric power produced in the state as well as imported from the Northwest. But reservoirs are drying up, with water levels falling so low in Lake Oroville that officials are weighing whether to idle the area’s hydropower plant for the first time.

“A second year of significantly lower than normal hydro conditions, virtually unchanged forecasted load levels under normal conditions, and increased possibility of extreme weather events indicate the ISO may still face challenges in meeting load this summer,” the California ISO noted in its report last month.

In wet years, hydroelectric power is a highly flexible resource, available to supplement other power sources when demand is high. A prolonged reduction in hydroelectric power makes it harder to deal with those surges.

“You can pick when you use it — you can save the water behind the dam and use that potential energy during the very worst times,” Williams said. “But you don’t know quite when the worst time is going to be.”

“A dry year means less water behind the dam,” Williams added, “and you have fewer bad days when you get to use that water.”