Western Heat Wave Tests California’s Clean Grid Transition

A heat wave across the Western U.S. this weekend will push California’s grid to the limits, as the state charts a course to eliminating fossil fuel power.

The weather forecast calls for several days of more than 100 degree Fahrenheit highs across the interior of the state, and close to that in coastal Los Angeles. The desert environment won’t cool down much at night, so air conditioning load is expected to crank continuously.

To prepare, grid operator CAISO issued a Flex Alert , asking customers to reduce electricity consumption during the late afternoon and evening Friday as the grid copes with “near-record or record-breaking heat.” Day-ahead power prices for Southern California hit their highest levels in two years, Bloomberg reported .

At the time of publication, CAISO expected peak demand of 47,641 megawatts, and counted 51,857 megawatts of capacity available. But there’s a literal asterisk attached to that latter figure: “available capacity varies due to outages, congestion and emergencies.” And solar production dips partway through the evening peak.

"We don’t call on consumers to conserve unless it's imminent that there could be an energy shortfall," said CAISO spokesperson Anne Gonzales. “If everybody conserves a little bit now, we don’t have to turn to more severe measures, such as rotating power outages.”

The Flex Alert is intended to broadcast that need, through CAISO’s social media presence, locals news coverage, and other partners like utilities. But it’s impossible to know what effect the alert has on people’s behavior, Gonzales noted. CAISO can’t determine if someone uses less because they saw the alert, or because they left the house for the evening.

California grapples with this heat wave in the midst of a historic shift from a grid that depends on natural gas for capacity to a system that eliminates carbon emissions by 2045. The state’s pre-eminent solar power fleet already meets much of demand during the sunny hours, but fades away as the sun sets. And flexible resources like batteries and controllable home devices are still in limited supply.

"It’s like a perfect storm in some ways," said Cisco DeVries, CEO of OhmConnect, which pays customers to reduce consumption during peak events. "This is definitely exposing the rough edges of our grid right now."

Capacity crunch

The state is shutting down some of the resources it used to ensure evening peak supply. California's last remaining nuclear plant, Diablo Canyon, is scheduled to shut down by 2025. Several large coastal gas plants are slated to end operations due to an environmental regulation on “once through cooling” technologies. California also depends on imports from neighboring states, which could be constrained due to air-conditioning demand in Nevada and Arizona as those states also experience intense heat.

"When it’s a localized heat wave, it’s not as hard on...