Undersea Volcano Test Produces Power, Startup Says

For 8.7 seconds last month, a generator on the sea floor produced more power than it consumed — the first fully encased well ever drilled at an underwater volcano, according to Seattle startup Endurance Energy.

In September, the company sailed 300 miles off the Oregon coast to a vent field roughly 5,000 feet underwater. There it drilled a two-inch-wide, 52-foot-deep well tapping 500-degree heat beneath the ocean floor. Then, as 10-foot waves battered the ship, the team lowered a three-ton generator to the sea floor.

The run didn't finish as planned. A power cable failed and stopped the experiment. But when engineers connected the generator to a natural vent, it briefly produced electricity. The company calls it proof that a network of undersea power plants could one day deliver baseload clean energy.

What makes this attempt different?

Small-scale tests have happened before. The scale has not. "No one's ever tried this even close to the commercial scale that we're going after," said Andrew Redd, founder and CEO of Endurance Energy.

Redd, a former SpaceX engineer, framed the venture as a talent play as much as an energy one. "I wanted to go after something that was going to be both really good for the world but also extremely compelling from an employee perspective," he said. "I looked around me and saw all of the hyper-capable people at SpaceX and posed the question, how do you get people like this to work for you?"

The math behind offshore geothermal is what drew him. Land-based geothermal needs permeable rock, high temperatures and water — and the ocean floor has all three in abundance.

"You've got this vast, permeable network on the mid-ocean ridges," Redd said. "You've obviously got unlimited water for your reservoirs. And then the crustal thickness is very low, so you've got this thin, oceanic crust that gives you a really high geothermal gradient."

How far along is the company?

Endurance Energy launched at the start of 2025 and has raised $63 million to date. The September test was its fifth undersea deployment and the first to run the company's full process end to end.

The prototype system, called Adélie, is back at the Seattle lab for tweaks ahead of a relaunch in a few months. In parallel, the company is developing a commercial-size, 2-megawatt generator.

Takeaway: an 8.7-second power surplus is a milestone, not a business — but it's the first hardware evidence the concept isn't pure theory.

What are the open questions?

Viability remains unproven, and two risks stand out:

• Environmental impact. The company, working with the University of Washington on early prototype tests, says drilling noise runs quieter than the ship's engine. Long-term effects are less clear, and permitting for full-sized commercial systems is an open question.
• Scale. Redd estimates roughly six terawatts could be developed around the Pacific's Ring of Fire over the next five years — more than current global demand — but only if the equipment to build it exists. That's a big assumption.

Still, Redd argues the economics favor the approach where resources sit near shore. "Where it's cost-effective, where there are resources near to shore, we'll be able to support a significant amount of the upcoming demand for baseload power, and then also start to displace existing power generation from non-renewable resources," he said. "That's really the mission of the company: to make offshore geothermal the economically obvious choice."

The company is building a modular system designed for factory replication. "That gets you into the realm of solar panel production, where it's the same thing being built over and over again," Redd said.

Where does the first plant go?

The first commercial project is planned in the Kingdom of Tonga, where much of the grid runs on imported diesel. If everything goes to plan, the plant could be running next year with the 2-megawatt generator.

That timeline — from an 8.7-second flash of net power to a diesel-displacing plant in roughly a year — is aggressive. The Adélie relaunch in a few months will show whether the September result was a proof point or a fluke.