Geothermal startup Mazama Energy raised $135 million in an oversubscribed Series B to develop horizontal wells in super-hot rock, with each well designed to generate up to 15 megawatts of electricity. The company plans to begin generating power sometime next year and says its first site in Oregon could produce 10 gigawatts, up from the 5-gigawatt potential cited last year by investor Vinod Khosla. Enhanced geothermal, which targets deeper and hotter rock than conventional projects, is emerging as a potential source of power for AI data centers and other large grid loads. Mazama has drilled beyond 10,000 feet in 15 days while targeting a depth of about 15,000 feet, where temperatures reach 750°F (400°C). At high pressure, water becomes a supercritical fluid that can absorb more energy than ordinary steam, allowing each well to produce up to 10 times more power than traditional geothermal technology, the company said. The University of Twente and the Clean Air Task Force estimate that tapping 1% of the world’s super-hot rock could generate more than 63 terawatts of electricity. Mazama has secured land for a second development and aims to complete its first site by 2030, when it says the project should generate 200 megawatts. Centaurus Capital and Doerr Capital led the funding round, which included ConocoPhillips, Shell Ventures, returning investors Khosla Ventures and Gates Frontier, and new investors SiteGround Capital, H. Barton Asset Management, and the Jeffrey and Marieke Rothschild Foundation. Mazama was incubated at Khosla Ventures.