The archive · Climate & Energy · Strategic decision · 2025–2026
Endurance Energy bets undersea volcanoes, not deep wells, unlock baseload geothermal
Ex-SpaceX engineer Andrew Redd's Endurance raised a $54M Founders Fund-led Series A to put geothermal plants on the ocean floor near spreading tectonic plates.
Endurance Energy
What the business is
Endurance Energy is developing seafloor geothermal power plants that tap heat where tectonic plates spread along the Pacific Ring of Fire, deliver electricity by submarine cable, and are installed and maintained largely by robotics.
Starting capital：$54M Series A led by Founders Fund, with Ascend, Construct Capital, Felicis Ventures, First Round Capital, Point72 Ventures, Riot Ventures and Voyager Ventures (announced June 2026).
How it started
After engineering Dragon and Starship at SpaceX, Andrew Redd wanted a renewable source that is available 24/7, non-polluting, quickly deployable and able to scale to tens or hundreds of gigawatts. He ruled out nuclear for regulatory and construction timelines, solar and wind for intermittency, and hydropower for scarce sites — leaving geothermal, which he notes supplies only about 0.4% of US energy. Rather than drill deeper on land far from cities, he founded Endurance Energy in 2025 to build plants at seafloor spreading zones near the Ring of Fire, a few dozen to a few hundred miles offshore.
What happened
Endurance grew to 25 employees, twelve from SpaceX, and completed four prototype deployments to deep-sea volcanic systems at depths up to 3,300 m and vent temperatures up to 386°C. In June 2026 it raised a $54M Series A led by Founders Fund, and earlier that year signed an agreement with the Government of Tonga to explore subsea geothermal in Tongan waters. The company planned to deploy a 100 kW generator at the Juan de Fuca ridge off the Pacific Northwest in fall 2026, with site selection balancing cable cost, resource scale and onshore market size while avoiding sensitive habitats such as hydrothermal-vent ecosystems.
How it ended up
Still pre-commercial as of 2026-09-02: four prototype deployments completed, a 100 kW seafloor generator slated for fall 2026 off the Pacific Northwest, and a Tonga exploration agreement signed.
Background
Endurance Energy, founded by former SpaceX engineer Andrew Redd, is developing geothermal power plants that sit on the ocean floor where tectonic plates spread — the Pacific Ring of Fire — instead of drilling thousands of feet into land-based hot rock like rivals Fervo and Zanskar. Redd's argument is that the best land sites are claimed or far from coastal population centers, while spreading seafloor ridges already bring magma close to the surface.
The company raised a $54M Series A led by Founders Fund in June 2026, bringing together a team of 25, twelve of them ex-SpaceX, to attack what Redd calls the only deployable, 24/7 renewable. He estimates about 6 terawatts of subsea geothermal could be developed in five to ten years — roughly a third of the world's current average energy use — enough to power major coastal cities on the Ring of Fire.
The engineering claim rests on offshore experience: Endurance has already completed four prototype deployments to deep-sea volcanic systems at depths up to 3,300 meters and temperatures to 386°C, and planned a 100 kW generator at the Juan de Fuca ridge off the Pacific Northwest for fall 2026. It also signed an agreement with the Government of Tonga to explore subsea geothermal in Tongan waters. The unproven parts are economics — submarine cables, corrosion, robotics — and whether the resource can be delivered to big onshore markets at competitive cost.
What has to be true
- First principles over incrementalism: Redd screened every energy source against 24/7 availability, pollution, speed and scale before choosing ocean geothermal.
- Spreading plates put heat within reach of the seafloor, avoiding the deep-drilling arms race that defines land geothermal.
- SpaceX and offshore oil-and-gas experience gives a young team credibility for extreme underwater engineering.
- The timing bet is real: surging AI data-center, EV and industrial demand makes 24/7 baseload power scarce and valuable.
- The risks are equally concrete: subsea power delivery cost, corrosion and pressure hardening, and proximity to sensitive marine habitats.
What can be applied
Sometimes the constraint isn't physics but where an industry looks: an incumbent approach (deep land drilling) can leave an entire resource class untouched until someone reframes the problem.
Aftermath
As of 2026-09-02 Endurance is pre-commercial but progressing: four prototype deployments to deep-sea volcanic systems (3,300 m, 386°C), a $54M Founders Fund-led Series A closed in June 2026, a 100 kW generator planned at the Juan de Fuca ridge in fall 2026, and a Tonga exploration agreement. Redd says Endurance will avoid hydrothermal-vent ecosystems, and a blowout would leak hot water into an ocean already venting terawatts. The 25-person team, twelve ex-SpaceX, is scaling offshore capability; the open question is whether seafloor geothermal beats land drilling and nuclear on delivered cost.
Sources
- Endurance Energy raises $54M to harness a massive untapped energy source
- Endurance Energy completes $54 million funding round to develop subsea geothermal technology
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