A California reactor that went dark in 1989 is about to store power instead of make it.
The Sacramento Municipal Utility District is developing a 160-megawatt, 640-megawatt-hour battery energy storage system at its Rancho Seco site near Herald. The project is in late-stage pre-construction, with work expected to start in late 2026, and includes new switchgear, backup generation and microgrid upgrades.
Storage on a Nuclear Brownfield
Four hours of storage lets SMUD shift midday solar into the evening peak, when demand climbs and the panels quit. The utility has leaned on batteries to push toward a zero-carbon grid by 2030, and Rancho Seco is one of the larger pieces. Details on the Rancho Seco battery project are here.
Why the Site Works
The old plant left behind exactly what a battery farm needs: high-voltage transmission ties and a switchyard already wired into the grid. Reusing that hardware trims interconnection cost and cuts months, sometimes years, off a schedule new greenfield storage can’t match.
Fitting a Cleaner Grid
As California retires gas plants and adds wind and solar, the problem shifts from making power to holding it for the right hour. Decommissioned energy sites with live grid connections are turning into some of the most valuable land for storage. Rancho Seco shows a shuttered reactor can still earn its keep.
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