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Sunrun and Tesla home batteries send a record 580 MW to California's grid

About 110,000 Powerwalls and 30,000 other home batteries discharged more than 580 MW during a Sept. 9 heatwave, the largest virtual power plant dispatch on record.

By Greener Numbers Editorial Team · Published September 24, 2026 · Updated 9/24/2026

Home batteries across California sent more than 580 MW of power to the grid on the evening of Sept. 9, the largest virtual power plant dispatch on record, according to Energy-Storage.News. That is enough to power every household in Sacramento County during peak hours.

Sunrun and Tesla ran the event over three evening hours at the request of the California Energy Commission and utilities, during a stretch of extreme heat, high demand and higher wholesale prices. Of the 580 MW, 517 MW came from Tesla Powerwalls and 63 MW from other batteries. About 110,000 Powerwalls took part, more than half of them owned and operated by Sunrun, and Sunrun also dispatched over 30,000 batteries from other makers.

The power flowed through two state programs: the Energy Commission's Demand Side Grid Support program and the CPUC's Emergency Load Reduction Program. The next evening, Southern California Edison asked for another three-hour dispatch, and the companies delivered more than 140 MW. Together the two nights would have topped 720 MW.

A Brattle Group report commissioned by Sunrun and Tesla estimates programs like these could save Californians up to $206 million in net costs by 2028. Participants are also paid for the power they share.

Two related bills cleared the legislature this month. SB 913 would have the CPUC set a way to value home batteries that export power during grid stress, and SB 905 would create a metric for how fully each part of the distribution grid is used. At the same time, the Newsom administration has blocked efforts to extend funding for the Demand Side Grid Support program.

Official source: Energy-Storage.News ↗