Mazama Energy, a developer of enhanced geothermal systems in superhot rock, announced on 17 September 2026 that it had raised $135m in new capital, including an oversubscribed Series B round.
Centaurus Capital, the investment firm founded by John Arnold, and Doerr Capital co-led the round. ConocoPhillips and Shell Ventures joined as new investors, while Khosla Ventures and Gates Frontier invested again. SiteGround Capital, H. Barton Asset Management and the Jeffrey and Marieke Rothschild Foundation also took part.
The company did not disclose a valuation or its total funding to date.
“We are now driving that integrated system toward greater speed, efficiency and scale. That is the foundation for commercial superhot power.”Sriram Vasantharajan, CEO, Mazama Energy
What Mazama does
Mazama, which is based in Frisco, Texas, and was founded in 2023 according to Canary Media, builds engineered geothermal systems: it drills into hot, dry rock and creates a reservoir that water can circulate through to bring heat to the surface. Its pilot site is near Newberry Volcano in Oregon.
In 2025 the company built an engineered geothermal system at 331°C (629°F) at Newberry, which it describes as the hottest built so far. It is now drilling a second well, called Project Athena, about a mile deeper, aiming for about 400°C (750°F). Mazama says a well at that temperature can deliver up to ten times the power of a conventional 200°C well.
According to Canary Media, the company's first well reached 10,350 feet and its second reached the same depth about 80% faster. ESG Today reported that Mazama also claims its approach uses 75% less water and 80% fewer wells than conventional geothermal projects.
What the money is for
The funding will go mainly to Project Ceres, which is supported by the US Department of Energy. The project is meant to develop horizontal wells in superhot rock and show about 15 megawatts of electric capacity per well, with power generation targeted for 2027. Canary Media reported that drilling of the Ceres wells was due to start later in 2026, with system testing in early 2027.
Mazama also plans to seek independent certification of more than 10 gigawatts of resource potential at Newberry, and it is evaluating other sites in the US and abroad, according to ESG Today and ThinkGeoEnergy.
Chief executive Sriram Vasantharajan, a chemical engineer who previously worked on complex oil and gas wells, said the company had shown drilling, reservoir creation and heat harvesting working together at Newberry. "We are now driving that integrated system toward greater speed, efficiency and scale. That is the foundation for commercial superhot power," he said.
Who invested
Mazama was incubated at Khosla Ventures, which backed the company again in this round alongside Gates Frontier. The arrival of ConocoPhillips and Shell Ventures brought two oil and gas companies onto the shareholder register.
John Arnold of Centaurus Capital said in a statement quoted by Canary Media that superhot geothermal offers the promise of firm, carbon-free power with a relatively small footprint. John Doerr, chairman of Doerr Capital, said the world needs much more electricity and needs to produce it cleanly and affordably, according to ESG Today.
The round came as investor interest in geothermal grew. ESG Today pointed to Fervo Energy's $1.9bn IPO as another sign of that interest.
Company website: mazamaenergy.com