Harnessing Earth's Fury: SMUD and Calpine's Bold Expansion at The Geysers Geothermal Field
Deep beneath the rolling hills of Northern California, a primordial force simmers—a vast reservoir of superheated steam, born from the planet's molten core. This is The Geysers, the world's largest geothermal complex, where the Earth's inner heat is tamed to power homes, businesses, and dreams of a cleaner future. In a significant step forward for renewable energy, the Sacramento Municipal Utility District (SMUD) and Calpine Corporation have announced an extension and expansion of their power purchase agreement (PPA) for geothermal energy from this iconic site. This partnership boosts capacity, fortifies the grid, and promises reliable, zero-carbon power for decades to come.
The Geysers' story blends natural wonder with human innovation. Revered for millennia, the area saw commercial geothermal power generation begin in 1960. Today, the field spans a vast area in the Mayacamas Mountains, featuring multiple power plants and hundreds of wells that tap into fractured rocks heated by ancient magma. Calpine operates the majority of the facilities, delivering around 725 MW of clean energy. In 2025, The Geysers proudly marked 65 years of sustainable power production.
At the core of this latest development is the renewed PPA between SMUD and Calpine. The agreement progressively increases SMUD's geothermal allocation from the current 100 MW to 150 MW, while extending the contract through 2042. This expansion leverages recent infrastructure improvements and new well drilling at the North Geysers, all designed to enhance output sustainably.
SMUD CEO and General Manager Paul Lau emphasized the strategic importance: “Expanding this partnership with Calpine supports our Zero Carbon Plan by bringing more dependable renewable energy to Sacramento, all while continuing to keep our rates among the lowest in California. We’re proud to lead the way toward a clean energy future that benefits both our customers and our region for generations to come.”
Calpine's Vice President of West Origination and Development, Gevan Reeves, added: “Geothermal energy from The Geysers plays a unique role in supporting grid reliability while helping California meet its clean energy goals. We’re proud to partner with SMUD to advance its zero-carbon vision continuing our commitment to the local communities in Lake and Sonoma Counties.”
What sets geothermal apart in the renewable mix? It delivers baseload power—consistent, 24/7 electricity with exceptionally high capacity factors—unlike weather-dependent solar or wind. Plants emit virtually no greenhouse gases during operation, use minimal land, and provide grid-stabilizing services like frequency regulation. In a state facing wildfires, droughts, and growing demand, this reliability is invaluable.
This deal aligns perfectly with SMUD’s ambitious 2030 Zero Carbon Plan, which targets complete elimination of greenhouse gas emissions from its power supply by the end of the decade. The plan emphasizes proven renewables like geothermal, alongside solar, wind, hydro, and massive battery storage, while phasing out natural gas generation.
Calpine, as the nation’s largest geothermal operator and owner of most plants at The Geysers, continues to invest in sustainability. Initiatives include reservoir recharge through effluent injection and careful well placement on existing pads to minimize environmental impact. Their long-standing operations reflect a dedication to both innovation and community benefit in Lake and Sonoma Counties.
This PPA extension points to a broader geothermal resurgence. With global capacity steadily growing and California already relying on geothermal for a significant share of its renewables, partnerships like this are accelerating the transition. Challenges such as upfront costs persist, but supportive policies and proven technology make geothermal increasingly attractive.
For SMUD’s customers in Sacramento, the benefits are clear: cleaner air, greater energy security, stable rates, and a stronger contribution to climate goals. As steam continues to rise from The Geysers’ ancient fissures, this collaboration lights the path toward a resilient, carbon-free energy future.
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