The Geysers adds 25 MW of geothermal capacity
Geothermal plant at The Geysers, California (source: Calpine)
Alexander Richter
8 Jun 2026
The Geysers geothermal complex in California has completed a 25 MW expansion, providing additional baseload renewable power for CPA and MCE customers.
California’s largest geothermal resource has added 25 MW of new generating capacity, further strengthening the role of geothermal energy in supporting grid reliability and clean energy supply across the state.
Calpine, a business unit of Constellation, announced the completion of the expansion project at The Geysers geothermal complex in Sonoma County, California. The additional capacity is expected to generate enough electricity to power more than 25,000 homes annually.
The project follows the commissioning of a 38 MW battery energy storage system at The Geysers in 2024, continuing investments aimed at supporting California’s growing demand for renewable electricity.
Power supply for Southern California and Bay Area customers
Of the newly added 25 MW, 18 MW will be supplied to Clean Power Alliance (CPA), one of California’s largest community choice aggregators serving customers across Southern California. The remaining 7 MW were brought online in 2025 and are being delivered to MCE, which serves communities in the San Francisco Bay Area.
“As California’s electricity demand continues to grow, investments in reliable, around-the-clock renewable energy are more important than ever,” said Aimee Blaine, Senior Vice President of Calpine’s geothermal region.
Matthew Langer, Chief Operating Officer of Clean Power Alliance, noted that geothermal energy remains an important component of the organisation’s clean energy portfolio because of its ability to provide continuous renewable electricity regardless of weather conditions.
Expanding the world’s largest geothermal complex
The expansion project included the construction of critical piping infrastructure and was completed under a Project Labor Agreement with local labour unions.
Located north of San Francisco, The Geysers is widely recognised as the world’s largest operating geothermal complex. The field has been producing electricity for more than 65 years by harnessing naturally occurring steam reservoirs beneath the surface.
Unlike intermittent renewable energy sources, geothermal power plants operate continuously and can provide stable baseload electricity throughout the day and night. This makes geothermal energy an increasingly valuable resource as California seeks to balance growing electricity demand with decarbonisation goals.
Calpine and Constellation continue to operate and invest in The Geysers as one of the most significant geothermal assets in the United States.
Source: company release/ Constellation
