Summary

Sunrun and Tesla say more than 140,000 home batteries supplied over 580 megawatts of peak power to California’s grid during a three-hour evening dispatch on September 9, 2026. The companies describe it as the largest residential distributed-power-plant event on record.

Sunrun and Tesla said their fleets of home batteries supplied more than 580 megawatts of peak power to California’s grid on the evening of September 9, 2026, during a period of extreme heat and high electricity demand. More than 140,000 batteries participated in the three-hour dispatch.

The companies describe the event as the largest residential distributed-power-plant dispatch on record. At 580 MW, the combined output was comparable to the capacity of a large power plant and, according to Sunrun, enough to power all households in Sacramento County during peak hours.

Contents

How the battery dispatch worked

The batteries were called on at the request of the California Energy Commission and utilities through two statewide grid programmes: the Demand Side Grid Support programme and the California Public Utilities Commission’s Emergency Load Reduction Program.

The participating systems were spread across California and included customers in the service territories of all three investor-owned utilities. The Demand Side Grid Support event was triggered after the California Independent System Operator’s day-ahead locational marginal price exceeded $200 per megawatt-hour. Pacific Gas and Electric Company separately called an Emergency Load Reduction Program event for batteries in its territory during the heat wave.

Tesla Powerwalls supplied 517 MW of the combined 580 MW. The event included 110,000 Powerwalls, 55% of which were owned and operated by Sunrun. Sunrun also dispatched more than 30,000 customer batteries made by other manufacturers.

A virtual power plant combines many smaller energy resources and coordinates them as a single grid resource. In this case, participating home batteries discharged electricity during the evening peak, when demand and wholesale prices were elevated. The arrangement allows batteries installed primarily for household backup and energy management to provide a grid service as well.

What made the event significant

The dispatch demonstrates the scale that distributed storage can reach when thousands of systems respond together. Instead of relying only on large generators, utilities and grid operators can draw power from batteries located across many homes. The distributed arrangement can add capacity near demand and give participating households a way to receive compensation for electricity shared with the grid.

Sunrun said the batteries were dispatched to increase the grid’s operating margin and put downward pressure on real-time energy prices. The company also argues that coordinated home systems can reduce the need for some new transmission and distribution infrastructure. Those are system-level benefits in addition to the household uses cited in the announcement, including outage protection and energy independence.

The event was not the maximum combined dispatch available from the two companies’ fleets. On September 10, Southern California Edison requested a separate three-hour peak-period dispatch, during which Sunrun and Tesla delivered more than 140 MW. Sunrun said that if the September 9 and September 10 resources had been called on the same evening, the companies could have delivered more than 720 MW in a single dispatch. That figure is a potential combined capability, not the output of one event.

The next expansion of distributed capacity

A report commissioned by Sunrun and Tesla from The Brattle Group estimated that programmes of this kind could provide up to $206 million in net cost savings to Californians by 2028. The announcement says the savings would benefit all grid-connected customers, while participating battery owners would receive direct compensation.

Sunrun, Tesla and Renew Home are also pursuing an initiative intended to unlock more than 16.8 gigawatts of flexible capacity from home batteries, solar systems, smart thermostats and electric vehicles for hyperscalers and utilities. Earlier in September, the companies announced plans to enrol nearly 21,000 existing flexible energy devices into a Google-funded distributed power plant with Pacific Gas and Electric. The resource is expected to begin supporting the grid as early as fall, according to Sunrun.

The 580 MW figure and the record description come from Sunrun’s September 21 company announcement. The release reports peak power for the dispatch and a three-hour operating window, rather than a total energy figure for the event.

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