The first-stage alert began at 6 p.m., when California ISO’s operating reserves stood at 12 percent, said David Marcus, an energy consultant and former adviser at the California Energy Commission. Its standard for the first stage had been 8 percent, according to the grid operator’s 2019 resource assessment.
The second stage began at 6:25 p.m., when its operating reserves stood at 9.59 percent, Mr. Marcus said. California ISO listed that stage in its assessment at 6 percent.
The final stage, 3, the rolling blackouts, began at 6:30 p.m., when operating reserves dipped to 8.9 percent but still above the 3 percent level that the operator listed last year, Mr. Marcus said.
“It’s just misleading to say that it was because it was a hot day,” Mr. Marcus said. “I think they were being overly cautious.”
Saturday’s peak demand, according to Mr. Marcus, reached 44,947 megawatts, much lower than the 46,797 he saw on Friday. But both of those amounts fell below the peak year for electricity use, 2006, when demand reached 50,270 megawatts, followed by 2017 with 50,116, according to data from California ISO.
As California ISO began taking its emergency actions on Saturday, electricity wholesale costs jumped on its energy market. The prices fluctuate based on how much electricity must pass through the wires. The more electricity that must get through a particular line, the higher the price, much like increased toll prices on a highway during traffic congestion.
Prices in locations near the Tahoe area across the state line to Reno and Carson City, Nev., spiked into the thousands of dollars per megawatt-hour, far above the typical costs of under $100.