Endurance Energy raises $54m to tap geothermal power beneath the ocean floor

Seattle-based clean energy startup Endurance Energy has raised $54 million in a Series A funding round to pioneer a completely untapped frontier in renewable energy: harvesting geothermal power from the ocean floor. The funding round was led by Peter Thiel’s Founders Fund, alongside significant investments from Felicis, Voyager Ventures, Riot Ventures, and Construct Capital. Returning seed backers Point72 Ventures, First Round Capital, and Ascend also participated.

Endurance, which was founded in 2024, plans to use the massive capital injection to scale its marine engineering teams and transition its specialized drilling hardware from early prototypes to full-scale, grid-connected systems.

Applying the SpaceX playbook to clean tech

What is generating massive buzz around Wall Street and Silicon Valley is Endurance’s leadership team. The startup was founded by Andrew Redd, a former SpaceX engineer who spent years working on the Dragon and Starship programs.

Out of the company’s 25 employees, nearly half are veterans of Elon Musk’s aerospace firm, while the vice president of engineering was pulled directly from the nuclear fusion startup Helion Energy. Redd emphasizes that this specific engineering background gives Endurance a unique competitive edge.

The team is explicitly adapting the hardware iteration, automated testing, and rapid deployment playbooks developed at SpaceX to build heavy industrial machinery capable of operating under the extreme pressures of the deep sea.

Targeting the Pacific ring of fire

Unlike conventional land-based geothermal startups that drill thousands of feet into continental rock, Endurance is heading directly to the sea. The company is targeting oceanic tectonic plate boundaries, specifically around the Pacific Ring of Fire, where tectonic plates split apart and Earth’s magma sits incredibly close to the ocean floor.

At these subsea volcanic sites, the surrounding water is naturally superheated to temperatures exceeding 728 degrees Fahrenheit (386 degrees Celsius). Endurance's proprietary technology involves anchoring specialized, ruggedized platforms to the seafloor that drill into these extreme thermal fields, using the intense heat to spin high-pressure turbines and generate massive amounts of continuous electricity.

Timeline to the grid

The influx of capital comes at a critical moment for the global energy sector, as tech giants struggle to find enough continuous, carbon-free electricity to power their massive new artificial intelligence data centers. In fact, a conceptual long-term application for Endurance involves co-locating subsea server modules directly with the ocean-floor generators, entirely eliminating the need for onshore grid tie-ins.

Endurance has already successfully deployed four material-testing prototypes to underwater volcanic systems at depths of up to 1,000 feet. The company's next major milestone is scheduled for this autumn, when it plans to deploy its first complete, end-to-end 100-kilowatt generator, dubbed "Adelie."

The Adelie system will be lowered onto the Juan de Fuca ridge, an active underwater volcanic range located off the coast of Washington and Oregon. The test will mark the first time a single subsea unit successfully handles automated drilling, power generation, and energy transfer back to the mainland. If successful, Endurance claims it has a clear line of sight to delivering gigawatt-scale electricity directly to the commercial power grid within the next two years.