Mazama Energy, a geothermal startup backed by prominent venture firm Khosla Ventures, has raised $135 million to advance its bet on superhot rock energy, according to TechCrunch. The company's approach involves drilling roughly three miles underground to reach rock formations hot enough to generate electricity at a scale that conventional geothermal projects rarely achieve.
To understand why this round is drawing attention, it helps to step back and look at where geothermal sits in the broader energy landscape. Traditional geothermal power has long occupied a frustrating position: technically proven, carbon-free, and capable of running around the clock regardless of weather, yet consistently overlooked in favor of solar and wind. The reason is mostly geological. Conventional geothermal depends on finding places where heat is naturally close to the surface and water is already present to carry that heat upward. Those conditions are rare, which is why geothermal has remained a niche contributor to global electricity supply for decades despite its theoretical promise.
The emerging category sometimes called enhanced or next-generation geothermal sidesteps that constraint by drilling far deeper, into what researchers call superhot rock — formations where temperatures are extreme enough to push energy output well beyond what shallower wells can deliver. The physics matter here. At the temperatures found several miles underground, water reaches a supercritical state, meaning it behaves neither as a liquid nor a gas in the conventional sense. That supercritical fluid can carry vastly more energy per unit volume than ordinary steam or hot water, which is why TechCrunch's report of a single Mazama well producing 15 megawatts continuously is significant. A single conventional geothermal well typically produces a fraction of that. The comparison to solar is also instructive: a solar installation rated at 15 megawatts only produces near its rated capacity for a portion of the day, while a geothermal well, by its nature, runs at full output around the clock.
Mazama is not alone in pursuing this direction. Several other startups have emerged in recent years with similar ambitions, and some are backed by overlapping pools of capital drawn from the technology venture world. Fervo Energy, perhaps the best-known name in next-generation geothermal, has used techniques adapted from the oil and gas industry — horizontal drilling, hydraulic stimulation — to unlock geothermal resources in places where they would otherwise be inaccessible. Quaise Energy has taken a more radical approach, exploring whether millimeter-wave energy beams could vaporize rock and allow drilling to depths that mechanical bits cannot easily reach. Mazama's particular focus on superhot rock at three miles depth places it in a distinct but related part of this emerging field, one where the engineering challenges are significant but the potential energy density is correspondingly higher.
The involvement of Khosla Ventures is itself a signal worth reading carefully. The firm has a track record of placing early, high-conviction bets on hard-technology categories that other investors consider too capital-intensive or uncertain, and it has occasionally been early enough to help define an entire sector. A $135 million round at this stage suggests the investors believe Mazama has cleared enough technical risk to warrant committing serious capital to drilling campaigns, which are inherently expensive and slow relative to software investments.
The likely consequences of this funding extend in several directions. For the geothermal sector broadly, a high-profile round at this scale continues to signal to other investors that deep drilling is worth taking seriously, which could attract additional capital and accelerate the development of specialized equipment and services that the whole sector needs. For the electricity grid, the 24/7 nature of geothermal output makes it genuinely complementary to wind and solar in a way that batteries and demand response have struggled to match fully. Grid operators and utilities looking for firm, dispatchable clean power have limited options at the moment, and a demonstrated superhot rock well producing 15 megawatts continuously would represent a credible new entry in that scarce category.
The risks, however, are real. Deep drilling is expensive and the subsurface is unpredictable. Projects that look viable based on geological models have historically surprised developers in costly ways. The $135 million will be consumed relatively quickly by drilling campaigns and well construction, and the path to commercial-scale deployment will require considerably more capital if the initial wells perform as expected.
What to watch for next is fairly clear. The most important near-term indicator will be whether Mazama's initial wells hit their performance targets — whether the geology at depth matches the models, whether the wells sustain output, and whether the cost per megawatt-hour of electricity produced falls into a range that can compete with other clean energy sources without heavy subsidy. If the technical results are strong, a much larger follow-on raise and potential utility partnerships become the logical next chapter. If the wells underperform, the company will face hard questions about whether the superhot rock thesis can be made economically viable at the drilling depths and costs current technology requires.
