Spencer Jackson spent seven years at SpaceX helping build some of the world's most audacious rocket engines. Now he's applying that aerospace rigor to a far earthier problem: the machines that turn underground heat into electricity.
His Hawthorne, California startup, Critical Energy, closed $22 million in early financing this week—$19 million in seed equity and $3 million in venture debt from Silicon Valley Bank. The round, co-led by Susa Ventures and Upfront Ventures, is betting that geothermal's biggest obstacle isn't finding heat beneath the earth's crust. It's waiting months or years for the industrial turbines that convert that heat into power.
Jackson's solution? Build them in a factory, ship them in standard shipping containers, and install them in weeks. "Think of it as flatpack energy infrastructure," he said in an investor disclosure dated June 17-18, though the analogy undersells the engineering complexity involved.
The financing—disclosed across multiple filings and confirmed by participants including MaC Venture Capital, Susquehanna Sustainable Investments, Humba Ventures, Scribble Ventures, and Underground Ventures—ranks among the heftier seed rounds for climate hardware in recent memory. BoxGroup, Climate Capital, Liquid 2 Ventures, Ritual Capital, Clocktower Ventures, and NosTerra Venture Capital also joined, according to documentation reviewed by investors.
For a company building turbomachinery for a niche corner of the energy market, the $19 million equity tranche across multiple seed rounds is unusual. Then again, geothermal is having a moment.
From Rockets to Rock Heat
Jackson's trajectory mirrors a broader Silicon Valley pattern: take lessons from aerospace's high-stakes engineering culture and transplant them into climate tech. Before incorporating Critical Energy in May 2024, he worked on Falcon Heavy, Starship, and Raptor engine programs at SpaceX. He later served as Entrepreneur in Residence at NosTerra Ventures, where the geothermal thesis apparently stuck.
The company's flagship product—dubbed "Apex"—is a closed-loop turbine system designed to sit atop geothermal wells or, eventually, scavenge waste heat from data-center gas turbines. No surface emissions. No consumables. Critical Energy has already demonstrated a small-scale prototype exceeding 50 kilowatts, validating the core design with a custom turbine assembly.
The fresh capital will fund the company's first 2.5-megawatt modular unit, targeted for completion sometime in 2027. A larger 5-megawatt module tailored for enhanced geothermal systems—the next-gen drilling techniques that don't require naturally occurring hot reservoirs—is also in the works. Specific project sites and power purchasers remain under wraps, perhaps deliberately so.
Bottlenecks, Everywhere
Jackson's pitch hinges on a supply chain headache that's plaguing more than just geothermal. Across the power grid, equipment shortages are slowing everything from transformer deliveries to natural gas turbine installations. For geothermal developers—especially those experimenting with enhanced drilling in new geographies—turbine lead times have become a genuine constraint.
"The wells are getting drilled. The financing is flowing. But you can't turn on a power plant without the generation equipment," one industry observer noted, speaking on background. Critical Energy is wagering it can shorten that timeline by an order of magnitude, manufacturing units in Hawthorne and delivering them as modular blocks.
Whether that model scales remains an open question. Factory assembly works beautifully for standardized products; geothermal projects, by contrast, tend to be bespoke, with temperature, pressure, and geology varying wildly site to site. Jackson's team will need to prove that modular design can accommodate that variability without sacrificing efficiency.
Policy Winds and Power Hunger
The timing, at least, seems fortuitous.
Geothermal has crept back into the policy conversation. The Department of Energy earmarked up to $171.5 million for next-generation field tests and exploration drilling in an announcement on February 25, while tax credits for zero-emissions generation—finalized in early 2025—now explicitly cover geothermal under a technology-neutral framework.
More tangibly, data centers are hunting for firm, always-on clean power at scale. Google signed a 150-megawatt geothermal power purchase agreement with Ormat for a Nevada site in February. Around the same time, Controlled Thermal Resources unveiled plans for a 600-megawatt geothermal complex in California's Salton Sea, explicitly targeting data-center demand. Enhanced geothermal upstarts Fervo Energy and Sage Geosystems have collectively pulled in more than half a billion dollars over the past eighteen months or so, signaling investor appetite for the category.
Still, geothermal remains a fraction of the grid. And turbine manufacturing, even modular turbine manufacturing, is capital-intensive and operationally unforgiving. Jackson's aerospace pedigree may help—SpaceX is famous for iterating fast and tolerating early failures—but energy infrastructure doesn't forgive mistakes the way a rocket test stand might.
Building Out in Hawthorne
Critical Energy is now staffing up at its Southern California facility. The leadership roster includes Steve Kohr as Head of Engineering, Tyler Rowan overseeing build and test operations, and Pete Perrone serving as fractional CFO. Advisors drawn from BCG, ConocoPhillips, and other corners of the energy-industrial complex round out the bench.
The company's 2027 target for its first commercial installation is ambitious but not outlandish, assuming supply chains cooperate and the turbine design translates smoothly from prototype to production unit. Jackson has framed the effort as both a manufacturing problem and a deployment problem—build faster, yes, but also make installation simple enough that geothermal developers aren't waiting months for specialized commissioning crews.
If the bet pays off, Critical Energy could become the go-to turbine supplier for an industry that's poised to expand but lacks the hardware to do so quickly. If it doesn't—well, the geothermal graveyard is littered with promising startups that underestimated how hard it is to build industrial equipment at scale.
For now, Jackson has the capital and the team. What comes next is the hard part: proving that factory-made turbines can actually solve a problem the rest of the geothermal industry hasn't quite figured out how to crack.
