Seafloor Geothermal Plant Briefly Tops Power Use
Endurance Energy's research-stage prototype points toward commercial seafloor power, with a Tonga installation targeted for 2027.
Updated on Nov. 3, 2026 in Energy
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Endurance Energy's Adélie subsea geothermal plant generated more electricity than it consumed for 8.7 seconds during a test at Axial Seamount, an active underwater volcano roughly 300 miles from Oregon. The technology is research-stage: the demonstration was a prototype test, not a commercial product, and the company is pursuing commercial power.
Why it matters
The test shows that seafloor hydrothermal vents might one day supply grid-scale power, a new energy source separate from land-based geothermal. Endurance is betting that the technology can eventually compete on cost in open electricity markets, though its first commercial installation is still ahead.
The prototype's measured median net output of about 2 kilowatts fell far short of its 100-kilowatt rating, while its peak reached 16.5 kilowatts. The figures come from a single short demonstration, so they describe what was achieved in one test rather than sustained performance.
The players
Endurance Energy
A Seattle-based startup developing subsea geothermal generation systems that harvest heat from seafloor hydrothermal vents.
Andrew Redd
Founder of Endurance Energy and a former SpaceX employee.
The details
The system draws superheated fluid from the seafloor, where hydrothermal vents heat water to about 538 degrees Fahrenheit, and converts that heat into electricity. Offshore seawater supplies cooling and pressurization for the subsea equipment. Early on, the plant could not draw enough fluid from a drilled 52-foot-deep well, so engineers moved it to a nearby natural vent. A software problem halted operations after the plant produced more power than it needed, and a failed power cable supplying the refrigerant pump ended the demonstration.
Timeline
January 2025: Endurance Energy is founded by Andrew Redd.
Within 16 hours of its first failed generation attempt, the Adélie system was retrieved, serviced, and redeployed to a seafloor vent.
2027: Endurance aims to deliver first power from a commercial installation in Tonga.
The Tech Race
Endurance's work moves geothermal generation from drilled land wells to natural seafloor vents, a departure from the conventional approach. The company's next milestone is the planned Gentoo test with redesigned subsea cables, tougher electronics, and deeper wells.
This is a research-stage prototype, so there is no product available to buyers or utilities today. The first commercial power is targeted for Tonga in 2027, and no pricing or grid-access details have been announced.
The takeaway
Watch whether Endurance's planned Gentoo test sustains net-positive output for longer than the 8.7-second window seen here. The Tonga installation targeted for 2027 will show whether the technology can operate as a commercial power source.
What happens next
Endurance plans to test Gentoo, an overhauled Adélie system, and aims to deliver its first commercial power in Tonga in 2027.
Further reading
For broader context on how heat-driven power is being pursued, explore our Energy coverage.
Source note: This article includes information reported by The Cool Down.
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