Constellation's Geothermal Play: 25MW Expansion Bolsters California Grid

MIDDLETOWN, CA – June 08, 2026 – In a significant move to enhance California's energy infrastructure, Calpine, a recently integrated business unit of energy giant Constellation, has completed a 25-megawatt (MW) expansion at The Geysers, the world's largest geothermal complex. The project, located in Sonoma County, injects a critical stream of reliable, around-the-clock renewable power into the state's increasingly strained electricity grid, capable of powering over 25,000 homes annually.

This strategic expansion is more than just an incremental increase in capacity; it represents a key investment in the type of power that experts say is essential for a stable energy future. The new output will primarily serve customers in Southern California through an 18 MW agreement with Clean Power Alliance (CPA), with the remaining 7 MW already supplying Bay Area customers via MCE since last year.

A Strategic Play for Grid Reliability

As California aggressively pursues its goal of 100% clean electricity by 2045, the grid faces a unique challenge: balancing the intermittent nature of solar and wind with a constant, growing demand. This is where the strategic value of geothermal energy becomes paramount. Unlike solar panels that go dormant at night or wind turbines that stand still on calm days, geothermal plants tap into the Earth's natural heat to generate power continuously, providing a firm, dispatchable source of baseload energy.

"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. "The Geysers is one of the nation's most important geothermal resources, and this expansion reflects our commitment to strengthening grid reliability while advancing California's clean energy goals."

This project doesn't exist in a vacuum. It follows the 2024 completion of a 38 MW energy storage system at the site, creating a powerful combination of steady generation and flexible storage. This dual approach allows the facility to not only provide constant power but also help stabilize the grid by absorbing excess energy and discharging it during peak demand, mitigating the price spikes often seen when solar generation wanes in the evening.

The Economic and Community Bedrock

Beyond its technical benefits, the expansion project underscores the potential for renewable energy to drive local economic growth and support skilled labor. The critical piping infrastructure for the project was built under a Project Labor Agreement (PLA) with local unions, ensuring that the work was performed by a highly skilled craft workforce under strong labor standards. This approach positions large-scale clean energy projects as a source of stable, well-paying jobs.

Partnerships with community-based energy providers like Clean Power Alliance and MCE are central to the project's impact. "Clean Power Alliance is committed to delivering dependable clean energy to our customers, and geothermal power plays an important role in providing around-the-clock renewable electricity," said Matthew Langer, Chief Operating Officer of Clean Power Alliance. "Partnerships like this strengthen California's clean energy future while supporting a more resilient and sustainable grid."

This sentiment is echoed by MCE, whose agreement for 7 MW of power also included $50,000 in community benefit funds from Calpine to promote local green jobs and clean energy access in underserved communities. The Geysers' operations are a significant contributor to the local economy, providing Sonoma County with approximately $1.1 million in annual royalties that support public safety, road maintenance, and other essential services.

Constellation's Geothermal Gambit

The project's completion comes just months after Constellation, the nation's largest producer of clean energy, finalized its acquisition of Calpine in January 2026. This expansion can be seen as an early proof point of the merger's strategic rationale: combining Constellation's vast resources and market presence with Calpine's portfolio of high-value, flexible generation assets. By investing in The Geysers, Constellation solidifies its leadership in a diverse clean energy portfolio that now prominently features geothermal alongside nuclear, hydro, wind, and solar.

For over 65 years, The Geysers complex has been a workhorse of California's power system. Spanning 44.5 square miles, its 13 power plants harness a rare geological phenomenon—dry steam reservoirs deep beneath the earth. The long-term sustainability of this resource is a testament to innovative environmental stewardship. Through partnerships with local counties, the complex receives treated wastewater via dedicated pipelines, which is then injected back into the reservoir to recharge the steam field, creating a unique and successful water recycling system.

The Future of Geothermal Power

While geothermal currently accounts for under 4% of California's electricity consumption, its role is set to expand dramatically. The California Public Utilities Commission (CPUC) has set goals to more than double the state's geothermal capacity by 2035, recognizing its unique value for grid reliability. This expansion at The Geysers is a step toward that future.

Further evidence of geothermal's growing importance can be seen in other recent agreements. The Sacramento Municipal Utility District (SMUD) recently expanded its power purchase agreement with Calpine, increasing its offtake from The Geysers to 150 MW and extending the contract to 2042 to support its own ambitious 2030 Zero Carbon Plan.

Looking ahead, the industry is buzzing with the potential of "next-generation geothermal" technologies, such as Enhanced Geothermal Systems (EGS), which aim to create reservoirs in hot rock formations that lack natural water or permeability. Initiatives like Sonoma Clean Power's "GeoZone" plan to develop 600 MW of enhanced geothermal power in the region, promising to unlock this energy source on a much wider scale. As Constellation and Calpine demonstrate with this latest milestone, the steady heat from beneath the earth is becoming an increasingly hot commodity in the business of clean energy.