California narrowly averted rolling blackouts Sunday night to relieve strain on its electric grid as parts of the state suffered record-breaking temperatures.
The California Independent System Operator, which operates much of the state’s electric grid, had anticipated a 4,000-megawatt power-supply shortage, driven in part by import constraints and wildfires affecting transmission lines in parts of the state. It called a Stage 2 emergency, urging utility customers to conserve power during the early evening hours, but stopped short of calling for rotating outages.
An extreme heat wave in the Southern half of the state sent temperatures in some areas above 120 degrees, forcing residents to shelter inside and crank their air-conditioning units, boosting electricity demand. As a result, the grid operator’s power-reserve margins wore thin at several points throughout the evening as solar generation began to decline.
Californians responded by conserving energy during the supply crunch, and the grid operator called off the emergency Sunday evening.
In addition to the heat threat, parts of the state may also face power outages throughout the week due to an expected windstorm. On Saturday,
which serves 16 million people in Northern and Central California, said it may pre-emptively cut power to about 103,000 customers in 17 counties starting Monday to reduce the risk that its electric equipment could spark wildfires.
The state grid operator last month called for rolling blackouts for the first time since 2001 as a heat wave swept California and other parts of the West. The state’s largest utilities cut power on two consecutive nights to several hundred thousand customers.
The second potential blackout threat in PG&E territory is a precaution against wildfires. California utilities in recent years have resorted to “public safety power shut-offs”—cutting off electricity to certain areas to reduce the risk of their power lines’ sparking wildfires when wind speeds pick up. Those safety measures are distinct from rolling blackouts, which gradually move through targeted cities and towns when power supplies get tight.
California has found itself strapped for electricity this summer during heat waves in the later hours of the day. To reduce carbon-dioxide emissions, the state has almost eliminated coal-fired generation and reduced its reliance on natural-gas power in favor of renewable energy.
That has posed a supply challenge when electricity demand spikes. Solar-energy production begins to decline in the early evening hours, when power usage peaks, reducing the capacity available during a supply crunch.
When demand surges, California relies more heavily on power imported from neighboring states, and natural-gas power plants capable of firing up quickly are kept on standby. But imports aren’t as readily available this weekend because the heat wave has strained supplies in other parts of the West, the grid operator said.
On top of that, wildfires in the Northern and Southern parts of California have affected transmission lines carrying power from hydroelectric plants and solar farms. On midday Sunday, the grid operator said it had lost as much as 1,400 megawatts of generation.
Write to Katherine Blunt at Katherine.Blunt@wsj.com
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