Endurance Energy Drills World's First Subsea Geothermal Well and Runs First Net-Positive Power Plant

Seattle startup drilled and completed the world's first subsea geothermal well, operated a power plant nearly a mile beneath the Pacific from Seattle, and demonstrated net-positive power from an active underwater volcano.

SEATTLE, Oct. 19, 2026 /PRNewswire/ -- Endurance Energy today announced the first end-to-end demonstration of subsea geothermal power: its Adélie test plant generated more electricity than it consumed on an active underwater volcano nearly a mile deep in the Pacific Ocean.

During a three-week deployment at Axial Seamount, 300 miles off the Oregon coast, Endurance drilled and completed the world's first offshore geothermal well, landed a 3-ton power plant on the seafloor, operated it in real time from Seattle over subsea fiber, and generated net-positive electricity from a nearby natural hydrothermal vent.

"On Sept. 27, we put a power plant on an active underwater volcano and made power," said Andrew Redd, founder and CEO of Endurance Energy. "This historic milestone is also our first end-to-end test. We now know, firsthand, what works at depth, what needs to be improved, and how to build the next system for sustained commercial generation."

Endurance calls the test deployment Adélie. It was designed to prove the full chain required for subsea geothermal power: drill a well, land and operate a power plant on the seafloor, convert geothermal heat into electricity, and communicate with the system from shore in real time.

The company was founded in January 2025 and made its first deep-sea deployment in August 2025. Adélie was Endurance's fifth deep-sea deployment in just over a year and its first to test all of these steps together.

When commercialized, subsea geothermal systems will convert the heat beneath the ocean floor into continuous, weather-independent clean electricity for coastal grids and industrial sites around the Pacific and worldwide.

What Adélie proved

A geothermal well could be drilled and completed on the seafloor. In the Axial Caldera, about 5,000 feet beneath the Pacific, Endurance's subsea lander drill bore two holes less than two feet apart. Both encountered hydrothermal fluid. The team cased and cemented the second hole, capped it with a valve, and completed a 52-foot (16-meter) geothermal well. After cementing, the well flowed at 260°C (500°F).

A power plant could be landed and controlled from shore. Endurance landed Adélie on target, then commanded the plant in real time from Seattle over the National Science Foundation's Regional Cabled Array, a seafloor fiber-optic network operated by the University of Washington as part of the Ocean Observatories Initiative. The team also tested optical and acoustic communications links and ran high-temperature hydrothermal fluid through the plant.

Subsea geothermal power could generate net-positive electricity. Connected to a nearby natural vent flowing at approximately 281°C (538°F), Adélie's turbine reached approximately 26,000 rpm. For 8.7 seconds, the system generated more electricity than it consumed—a median of about 2 kilowatts net and a peak of 16.5 kilowatts net.

"The main question we had is can the system generate more power than it uses." said Redd. "Adélie did. Goddard's first liquid-fueled rocket flew for two and a half seconds. Our first net-positive run lasted about nine. Our approach is to make it exist, then make it good."

What Endurance learned

Adélie was a test article, not a commercial-scale power plant. Its purpose was to expose the engineering realities of operating a geothermal system on the deep-ocean floor.

The newly drilled well delivered hot fluid but was too restrictive to run the plant. The net-positive run at the nearby natural vent ended when battery overcurrent protection stopped the system. About ten minutes later, during a restart attempt, a power cable feeding Adélie's refrigerant pump failed, ending the dive.

The deployment produced data on seafloor drilling, well flow, heat transfer, mineral buildup, high-temperature power generation, and long-distance control of subsea equipment, which is information Endurance will use to build its next system.

Drilling at depth

Endurance drilled away from the hydrothermal vent chimneys and the marine life that lives around them. Its well is approximately two inches wide; by comparison, oil, gas, and onshore geothermal wells often begin with casings 20 to 36 inches across.

The team used filtered seawater rather than drilling mud, avoiding the chemicals commonly used in offshore oil and gas drilling.

Environmental monitoring

Endurance ran a voluntary environmental monitoring program throughout the deployment. Before placing equipment, the team mapped the seafloor and selected the least disruptive site. It sampled water before and after every operation and recorded the surrounding seafloor community (including tubeworms, snails, crabs, and bacterial mats) on video during every dive.

The team checked its findings against 11 instruments operated by outside scientists. The loudest sound recorded was the ship's engine, within the normal range for research vessels at Axial Seamount based on three years of recorded data. No marine mammals were observed. Monitoring showed no unusual seismic or volcanic activity, no significant changes to the seafloor community, and no significant change to the site's natural hydrothermal activity.

More than 40 water, rock, and mineral samples are now with independent laboratories for analysis.

What's next

This winter, Endurance will deploy Gentoo, a refurbished and upgraded version of Adélie designed to target higher power and longer sustained generation.

While the Adélie well reached 16 meters (52 feet), Endurance's current lander drill can reach 80 meters (about 260 feet). The company expects deeper wells to deliver the greater flow needed for sustained generation. In parallel, Endurance is developing Leopard, its 2-megawatt commercial generator.

Endurance's first commercial project is in development in the Kingdom of Tonga, targeting first power in 2027. The project is intended to supply clean, always-on electricity directly to Tonga's grid, which today runs largely on imported diesel.

About Endurance Energy

Endurance Energy is a Seattle-based company developing the first commercial subsea geothermal power systems. Its modular generators sit on hydrothermal reservoirs along mid-ocean ridges and convert the Earth's heat into continuous, weather-independent electricity. That power can serve coastal grids, industrial sites, and data centers around the Pacific and worldwide. The company has raised $63M to date, including a $54M Series A led by Founders Fund. Learn more at enduranceenergy.com.

SOURCE Endurance Energy