California keeps retiring big thermal plants. It still needs somewhere to park power when the sun drops. SMUD’s answer sits on the footprint of a shuttered reactor.
The Sacramento Municipal Utility District is developing a 160-megawatt, 640-megawatt-hour battery energy storage system at the Rancho Seco site near Herald, where a nuclear plant ran until 1989. The project is in late-stage pre-construction, with work expected to begin in late 2026. Plans include new switchgear, backup generation and grid-integration upgrades.
Project Scope
Four hours of storage at 160 MW lets SMUD push midday solar into the evening peak and firm up its 2030 zero-carbon target. The reused site already carries transmission ties and a switchyard from its generating days, which trims interconnection cost and schedule.
Why It Matters
Brownfield energy sites with existing grid connections are turning into prime real estate for storage. Rancho Seco shows how a decommissioned reactor can get a second life without stringing new transmission. For SMUD, it’s another block in a portfolio that has to balance a grid leaning harder on wind and solar every year.
Project Team & Details
| Developer | Sacramento Municipal Utility District (SMUD) |
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| Owner / Client | Sacramento Municipal Utility District (SMUD) |
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| Status | Planned |
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| Funding Source | Public (Municipal) |
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