An analysis by The Brattle Group found that Sunrun’s fleet of home batteries across California was the largest contributor to a historic distributed power plant dispatch event that delivered an average of 535 megawatts to the grid—enough to power more than half of the city of San Francisco.
Multiple distributed power plant aggregators, of which Sunrun is the largest, discharged home batteries in coordination with the California Energy Commission, the California Independent System Operator and local utilities during a scheduled test. The event occurred between 7 and 9pm on Tuesday, July 29. The goal was to prepare for future green energy deliveries during heat waves in August and September.
According to The Brattle Group, output from more than 100,000 residential batteries resulted in “a visible reduction in net load” across the statewide grid when quality output is most critical.
“Performance was consistent across the event, without major fluctuations or any attrition,” said Ryan Hledik, principal at The Brattle Group. “Events like these demonstrate to system operators that residential batteries provide dependable, planning-grade performance at scale.”
Sunrun’s home batteries supplied more than two-thirds of the total energy dispatched during the event—averaging more than 360 megawatts over the two hours. Company officials say they could repeat this, if necessary, every day. Sunrun’s batteries acted in the same way as a traditional power plant and “decisively knocked down” the state’s evening peak demand for electricity, they added.
“This customer-led solution is a win-win for households and the grid,” said Sunrun CEO Mary Powell. “Distributed home batteries are a powerful and flexible resource that reliably delivers power to the grid at a moment’s notice, benefiting all households by preventing blackouts, alleviating peak demand and reducing extreme price spikes.”
This is the second time this summer that Sunrun’s fleet of home batteries helped reduce California’s peak energy demand. On June 24, Sunrun’s statewide distributed power plant dispatched 325 megawatts of peak power from 7 to 9pm.
