Subsea Geothermal Plant Briefly Generates Net Power
Endurance Energy's Adélie system produced more electricity than it consumed for 8.7 seconds during a test off Oregon.
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 100-kilowatt system delivered a median net power of about 2 kilowatts, with a peak of 16.5 kilowatts, before a software problem and a power cable failure ended the demonstration.
Why it matters
The test shows that geothermal energy can be harvested from the seafloor using offshore seawater for cooling and pressurization, a approach that could add a new source of electricity. Endurance says the technology must compete on cost in open electricity markets as it matures.
The field test produced net-positive output for 8.7 seconds, with a median net output of about 2 kilowatts against the plant's 100-kilowatt rating. The report does not say whether the system can maintain net-positive generation over extended operation or at what cost.
The players
Endurance Energy
Endurance Energy is a Seattle-based company founded in January 2025 to develop subsea geothermal power systems.
Andrew Redd
Andrew Redd is a former SpaceX employee who founded Endurance Energy in January 2025.
The details
Endurance Energy's initial well at Axial Seamount could not draw enough hydrothermal fluid from a 52-foot-deep bore, so engineers moved the plant to a nearby natural vent where the fluid measured about 538 degrees Fahrenheit. Within 16 hours of the first failed attempt, the company retrieved, serviced, and redeployed the Adélie system to the vent.
Timeline
January 2025: Endurance Energy was founded by Andrew Redd, a SpaceX alumnus.
Within 16 hours of the first failed attempt: Adélie was retrieved, serviced, and redeployed to a seafloor hydrothermal vent.
2027: Endurance aims to deliver its first commercial power from an installation in Tonga.
Big Picture
The Adélie test is the first reported net-positive generation from a seafloor geothermal system using offshore seawater for cooling and pressurization. Endurance's follow-on Gentoo system, with redesigned subsea cables and deeper wells, is intended to extend the approach toward commercial deployment.
If the approach proves cost-competitive, seafloor geothermal plants could eventually add a new source of electricity for coastal and island grids. Endurance's stated target is a commercial installation in Tonga in 2027, which would be the first test of that outcome.
The takeaway
Seafloor geothermal power has moved from concept toward field testing, but a single 8.7-second result is far from proof of commercial viability. Watch for longer-duration tests and cost data as Endurance advances its Gentoo system.
What happens next
Endurance Energy plans to test its Gentoo system and aims to deliver first commercial power in Tonga in 2027.
Further reading
Explore more on Energy developments like this one.
Source note: This article includes information reported by The Cool Down.
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