Mazama Energy raises $135m Series B for superhot geothermal push
Mazama Energy has closed a $135 million Series B to accelerate commercial development of what the Dallas-based developer describes as the world's hottest engineered geothermal system (EGS). The oversubscribed round was led by Centaurus Capital, founded by John Arnold, and Doerr Capital, with strategic investment from ConocoPhillips and Shell Ventures, and repeat participation from Khosla Ventures and Gates Frontier. Several family offices and foundations also joined the round.
The capital will fund Project Ceres, a US Department of Energy-supported programme aimed at demonstrating 15 megawatts-electric (MWe) of capacity per horizontal well and achieving power generation in 2027. Mazama says it is also targeting independent certification of more than 10 gigawatts-electric (GWe) of resource potential at its Newberry, Oregon site, while evaluating additional locations in the United States and internationally.
The technology
Engineered geothermal systems create underground heat reservoirs where none exists naturally, by drilling deep wells and fracturing rock to allow water circulation. Mazama's claim to distinction is operating at extreme temperatures: in 2025, it recorded a reservoir temperature of 629°F (331°C) at Newberry, a milestone it says no other EGS project has reached. Its current second well, Project Athena, reached the same 10,350-foot depth in roughly 15 days this month, around 80 per cent faster than the 2025 well, and is drilling a further mile toward a target of 750°F (400°C).
At that temperature, water enters a supercritical state with significantly higher energy density than conventional geothermal fluid. Mazama says the physics translates into up to ten times the power output of a conventional 390°F (200°C) well, allowing the same capacity to be delivered with 80 per cent fewer wells and 75 per cent less water. Those figures are the company's own projections and have not been independently verified.
CEO Sriram Vasantharajan said the Newberry results demonstrate the three critical capabilities in an integrated system: extreme-temperature drilling, reservoir creation, and heat harvesting. "That is the foundation for commercial superhot power," he said.
Market context
Geothermal power is a small but strategically significant slice of the firm, dispatchable clean-power market. Unlike solar and wind, it generates continuously regardless of weather, making it attractive to grid planners and corporate buyers chasing round-the-clock clean power. The sector has seen renewed capital interest as hyperscalers and utilities search for alternatives to gas peakers to back intermittent renewables.
Several well-funded competitors are active in the EGS and superhot-rock space, including Fervo Energy, which has agreements with Google and Nevada utilities, and Quaise Energy, which is developing millimetre-wave drilling technology for ultra-deep wells. The participation of ConocoPhillips and Shell Ventures signals that oil-and-gas majors, with deep expertise in subsurface drilling and reservoir management, are treating next-generation geothermal as a transferable-skills opportunity rather than a peripheral bet.
The broader capital environment for firm clean power has tightened in 2025 and 2026 relative to the post-Inflation Reduction Act (IRA) peak, but geothermal has benefited from sustained US Department of Energy support through its Enhanced Geothermal Shot programme, which targets an 90 per cent reduction in EGS development costs. Mazama's Project Ceres is part of that federal funding architecture.
Policy and commercial path
The IRA's technology-neutral clean-electricity production tax credit is available to geothermal generators, giving superhot-rock projects the same per-MWh subsidy runway as solar and wind. That policy parity, combined with the baseload profile, is what makes the economics credible to infrastructure-oriented investors.
Near-term milestones investors will track include: the Project Ceres power-generation demonstration in 2027, independent certification of the Newberry resource estimate, and the naming of any utility or corporate offtaker willing to sign a power purchase agreement. Mazama has not yet disclosed a commercial PPA or a project-level cost of energy.