Endurance Energy Secures $54 Million to Unlock a Vast Untapped Clean Energy Resource.

After spending years helping build rockets designed to travel beyond Earth, finding the next challenge was never going to be simple. For former SpaceX engineer Andrew Redd, the answer ultimately came from looking beneath the ocean rather than toward space.

Raised in the Pacific Northwest, a region that has experienced severe heat waves and devastating wildfires in recent years, Redd knew he wanted to focus his efforts on renewable energy.

“The experience at a very hardcore company like SpaceX made me realise that I can’t just come up with an incremental solution,” Redd said. “It actually has to be brand new, and it has to be approached from first principles.”

Redd, who worked on both the Dragon spacecraft and Starship programs during his time at SpaceX, left the company to launch Endurance Energy. The startup has now raised a $54 million Series A funding round as it pursues an ambitious goal: tapping into deep-ocean geothermal resources capable of producing terawatts of clean energy.

The financing round was led by Founders Fund and included participation from Ascend, Construct Capital, Felicis Ventures, First Round Capital, Point72 Ventures, Riot Ventures, and Voyager Ventures. The company plans to use the capital to advance the development of offshore geothermal power plants as electricity demand continues to rise from AI data centres, electric vehicles, and industrial operations.

Since establishing the company last year, Redd has expanded the team to 25 employees. Twelve of those staff members previously worked at SpaceX. Endurance’s vice president of engineering also brings experience from Helion Energy, a company focused on fusion power.

While geothermal energy itself is far from a new concept, humans have relied on Earth’s natural heat for thousands of years, whether through hot springs or modern geothermal power facilities. Redd, however, believed there was a significant opportunity that had largely gone unnoticed.

He approached the challenge by identifying several requirements for a future energy source. In his view, it must be renewable or at least non-polluting.

“That’s my non-negotiable,” said Redd, who serves as Endurance’s CEO.

He also believes the energy source must provide power around the clock, which the industry refers to as baseload generation. In addition, it needs to be deployable within a reasonable timeframe and capable of scaling to produce tens or even hundreds of gigawatts of electricity.

Using those criteria, Redd quickly eliminated several alternatives. Nuclear power, he argued, often faces lengthy regulatory reviews and construction schedules that can take years. Wind and solar generation depend on weather conditions and require battery storage to provide continuous power. Hydroelectric projects are geographically limited, and many of the most favourable locations have already been developed.

That left geothermal energy.

“Geothermal is the only real deployable, baseload renewable,” Redd said. “But why is it only 0.4% of U.S. energy?”

Several startups are already working to expand geothermal power, including Fervo and Zanskar. However, those companies generally need to drill thousands of feet into Earth’s crust to reach temperatures high enough to operate commercial power plants. As a result, many of the strongest geothermal opportunities have historically been concentrated in the western United States, far from major population centres.

The most desirable drilling locations—areas where the crust is thinner and magma lies closer to the surface, such as parts of Iceland and California—have long been recognised. More recently, companies including Fervo Energy, XGS Energy, and Sage Geosystems have pursued new approaches, but they still require drilling significantly deeper to access sufficient heat. Many of those resources remain distant from large urban markets.

According to Redd, one major opportunity has remained largely untouched: the oceans.

In several regions around the world, tectonic plates are gradually pulling apart, allowing hot magma to rise closer to the seafloor. Countries and regions located along the Pacific Ring of Fire—including the U.S. West Coast, Japan, and much of Southeast Asia—sit near some of the most geologically active zones on the planet.

Moving geothermal operations offshore introduces a variety of technical challenges. At the depths Endurance intends to target, underwater work becomes considerably more difficult. Much of the construction and maintenance will likely depend on robotic systems. Equipment must also withstand intense water pressure and the corrosive effects of saltwater, which can rapidly degrade conventional materials.

Redd believes those challenges can be overcome. He points to the oil and gas industry, which has spent decades developing technologies for deepwater drilling and offshore infrastructure.

He also argues that geothermal operations would present fewer environmental risks than offshore fossil fuel extraction.

“If we have a blowout — quote unquote — you’re leaking hot water into the ocean, which is already leaking out in terawatts all over the Earth,” Redd said.

Some of the geothermal sites Endurance is evaluating are located only a few dozen miles offshore, while others are situated several hundred miles from land. Determining which resources move forward will depend on an optimisation process that weighs multiple factors, including the cost of undersea transmission cables, the size of the geothermal resource, and electricity demand in nearby coastal markets.

Redd noted that the company intends to avoid environmentally sensitive regions, including areas surrounding hydrothermal vent ecosystems.

If Endurance succeeds in developing even a small portion of the available offshore geothermal potential, the resulting energy output could be substantial. Redd estimates that roughly 6 terawatts of geothermal capacity around the Ring of Fire could potentially be developed within the next five to ten years.

For comparison, global energy consumption averages around 20 terawatt-hours across all sources at any given time.

“The idea is that you could support any major coastal city on the Ring of Fire,” Redd said.