California issues rare warning of power shortfall amid heat

California’s grid operator is warning of potential power shortages that could lead to blackouts Wednesday as a heat wave mounts and a historic years-long drought has drained hydropower supplies.

Officials asked residents to conserve power Wednesday between 4 and 9 p.m. local time as temperatures soar above 100 degrees Fahrenheit (38 degrees Celsius). The California Independent System Operator, which runs the grid, warned on its website of possible power shortages during that time.

It’s the biggest test for California’s grid since the summer of 2020, when rolling outages engulfed portions of the state. It comes as Russia’s war in Ukraine triggers an energy crisis in Europe and as record temperatures driven by climate change tax grids around the globe.

“It’s pretty clear Mother Nature has outrun us,” California Governor Gavin Newsom, who issued an executive order Wednesday to free up emergency power supplies, said during a news conference. “The reality is we’re living in an age of extremes — extreme heat, extreme drought.”

The worst dry spell in 1,200 years has gripped nearly every inch of California with drought this summer, leaving rivers and reservoirs perilously low. That has significant implications for a state that generates about 10% of its electricity from hydroelectric dams and has aggressively closed natural-gas power plants in recent years.

California’s electricity demand is forecast to build over the next week and top 48 gigawatts on Monday and Tuesday, which would be the highest demand on the state grid since 2017, according to grid operator, known as Caiso. Officials are projecting a shortfall of contracted reserves — excess supplies kept on hand as backup to prevent blackouts– during some of the tightest hours starting Wednesday night.

“We’re seeing some supply uncertainties for later in the day, so we’re asking consumers to help stabilize the grid by conserving electricity,” Caiso spokeswoman Anne Gonzales said in an email.

The call for conservation comes hours before state lawmakers are expected to decide the fate of the state’s largest power-generating facility: the Diablo Canyon nuclear plant. The two atomic reactors — the last remaining ones in the state — are scheduled to close by the end of 2025. But Governor Gavin Newsom is pushing legislators to extend their lives by five years to shore up the grid against blackouts as the state transitions to renewable energy.

Owners of transmission lines and power plants have been requested to restrict maintenance during this heat wave and consumers may be asked repeatedly to conserve to help keep the grid stable, Caiso said. Demand will exceed the high that California ISO had projected for the summer of 45.5 gigawatts. It’s still short of the 2006 record of nearly 50.5 gigawatts. One gigawatt is enough to power about 750,000 homes in California.

“This is a manifestation of what Caiso warned folks about back in May, that unless they see voluntary curtailments the grid could become unstable during certain periods of high demand,” said Gary Cunningham, director of market research at risk management firm Tradition Energy. “In this case it is extreme heat that is causing it, but overall weakness in the supply picture are adding to the issue.”