Subsea Thermal Energy: A Seattle Startup Advances Volcanic Power for

A geothermal startup aiming to source energy directly from undersea volcanoes just hit a major milestone that could bring round-the-clock clean energy to cities on the northwest coast of the United States and serve as a critical proof of concept for other regions, with particular relevance for the other 14 countries situated along the Pacific Ring of Fire. Seattle-based energy startup Endurance Energy just announced that it successfully created net-positive energy from its underwater geothermal plant in a world first. The company successfully…

admin October 24, 2026

**Seattle Startup Achieves Breakthrough in Offshore Geothermal Power**

**By Haley Zaremba**
*October 24, 2026*

### Key Takeaways
* **Historic Milestone:** Seattle-based startup Endurance Energy successfully executed a complete drilling-to-electricity operational cycle on an active submarine volcano, generating net-positive power for the first time in history.
* **Remote Operations & Next Steps:** Engineers monitored and controlled the system remotely from mainland facilities. Endurance Energy is now preparing to deploy up to six container-sized, 2-megawatt generators off the coast of Tonga.
* **Economic & Strategic Context:** While experts note that marine operations carry higher initial costs than land-based setups, the U.S. Department of Energy projects next-generation geothermal could provide up to 90 gigawatts of capacity in the United States by 2050.

***

A major technological breakthrough in offshore renewable energy could soon provide continuous, zero-carbon power to coastal cities along the Pacific Ring of Fire.

Clean technology startup Endurance Energy announced it has successfully harvested net-positive power from a plant installed directly on an active underwater volcano. The achievement marks the world’s first end-to-end demonstration of subsea geothermal energy generation, spanning drilling, thermal capture, and electricity conversion.

While the net-positive power generation lasted under ten seconds during this initial test, company leadership emphasized the significance of validating the core design in extreme marine environments.

“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.”

### Remote Control and Marine Advantages

The test also validated the project’s logistics platform. Operators located at a command center in Seattle successfully started, managed, and shut down the submerged system remotely—tracking thermal levels and internal pressures in real time without requiring on-site divers or local offshore crews.

Deploying geothermal infrastructure on the ocean floor offers distinct physical advantages over traditional terrestrial facilities. Ambient deep-water temperatures provide a natural cooling system, while external hydrostatic pressure allows for significantly more compact plant engineering.

The startup is leveraging these design efficiencies for its next phase: deploying a commercial-scale project in the territorial waters of Tonga.

“The 2 MW commercial generators will be about the size of a shipping container, and we are deploying up to six of these generators off Tonga,” Redd stated. “The physical footprint of this project will be relatively small.”

### Capital Costs and Industry Outlook

Despite the physics-based advantages, submarine installations present severe engineering and maintenance hurdles that could inflate initial capital expenditures.

“It’s probably technically feasible, but it would undoubtedly be more expensive than to do it on land,” noted Roland Horne, a professor of energy science and engineering at Stanford University.

Nevertheless, interest in advanced geothermal technologies is accelerating globally. Rising power demand from artificial intelligence infrastructure and data centers has prompted tech firms and investors to seek baseload alternatives to intermittent wind and solar resources.

The sector also benefits from rare bipartisan alignment in U.S. energy policy. Next-generation geothermal relies heavily on directional drilling, fluid dynamics, and subsea engineering techniques adapted directly from the oil and gas sector.

“The U.S. has a number of different superpowers, and putting holes in the ground and taking things out of those holes is one of them—and doing so more economically and more efficiently than basically any other place on Earth,” said Drew Nelson, vice president at energy think tank Project InnerSpace.

According to baseline estimates from the U.S. Department of Energy, enhanced geothermal systems could supply up to 90 gigawatts of steady electricity to the domestic grid by 2050—enough capacity to supply roughly 65 million homes. Successful commercialization of subsea resources could expand that potential even further across coastal regions globally.