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Geothermal is too expensive, but Dig Energy’s impossibly small drill rig might fix that

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Geothermal is too expensive, but Dig Energy’s impossibly small drill rig might fix that Tim De Chant AM PDT · September 9, 2025 On a farm near Manchester, New Hampshire, I was recently treated to a gusher of dirty water, not exactly the sort of thing that most startups will show a

The startup, which has been operating in stealth for the last five years, developed the water-jet drilling rig in an effort to make geothermal heating and cooling so inexpensive that it will displace fossil fuel boilers and furnaces. The rig is central to that, promising to slash drilling costs

On Tuesday, Dig Energy emerged with $5 million in seed funding, TechCrunch has exclusively learned. The round was led

Heating and cooling represent about a third of all energy use in the U.S., and in data centers, the figure can be as high as 40%. Geothermal can slash HVAC energy use while also saving grid operators up to $4 billion annually. To help stabilize its creaking electrical grid, the U.S. needs to drill 6 million feet of geothermal borehole daily through 2050, according to the Oak Ridge National Laboratory.

But geothermal doesn’t come cheap, at least not at first.

“In the United States, geothermal has been 1% of building installations for decades,” Dig co-founder and CEO Dulcie Madden told TechCrunch. That’s despite the technology’s low operating costs. “It’s really just because upfront cost is so, so, so expensive.”

There are two main flavors of geothermal: Enhanced geothermal drills down thousands or tens of thousands of feet. Companies like Fervo and Quaise that are drilling the deep are tapping very hot temperatures — usually in the hundreds of degrees — to generate electricity. The other, shallow geothermal, which is what Dig is focused on, is usually limited to hundreds of feet. At those depths, the ground maintains a consistent temperature year round, which is perfect for heating and cooling residential and commercial buildings.

Techcrunch event Join 10k+ tech and VC leaders for growth and connections at Disrupt 2025 Netflix, Box, a16z, ElevenLabs, Wayve, Sequoia Capital, Elad Gil — just some of the 250+ heavy hitters leading 200+ sessions designed to deliver the insights that fuel startup growth and sharpen your edge. Don’t miss the 20th anniversary of TechCrunch, and a chance to learn from the top voices in tech. Grab your ticket before Sept 26 to save up to $668. Join 10k+ tech and VC leaders for growth and connections at Disrupt 2025 Netflix, Box, a16z, ElevenLabs, Wayve, Sequoia Capital, Elad Gil — just some of the 250+ heavy hitters leading 200+ sessions designed to deliver the insights that fuel startup growth and sharpen your edge. Don’t miss the 20th anniversary of TechCrunch, and a chance to learn from the top voices in tech. Grab your ticket before Sept 26 to save up to $668. San Francisco | October 27-29, 2025 REGISTER NOW In shallow geothermal, pipes carry water underground where it transfers heat to or from the earth. In the summer, it dumps excess heat, and the chilled water returns to the surface to cool a building. In the winter, it absorbs heat to warm it.

Installing the ground loop, as the underground piping is called, represents around 30% of the total cost of a ground-

“When we were getting started, we were like, can we build a lower-cost drill?” Madden said.

Madden and her co-founder, husband Thomas Lipoma, began exploring the space five years ago after winding down their previous startup, Rest Devices. They soon stumbled upon old research describing how to use water jets instead of traditional cutting bits to bore into the Earth.

But while there had been plenty of research into the technology, it still wasn’t ready for prime time. “A lot of the drilling technology has trickled down from oil and gas,” Madden said. Translation: It tends to be large, expensive, and overpowered for something like geothermal at the depths Dig is plumbing.

Dig has spent years refining the design of its rig, drilling test holes near its offices in New Hampshire. They’ve drilled through soil, gravel, clay, sand, and a range of different rock types, including sandstone, limestone, granite, slate, and shale. The team showed me test blocks of some very dense rock with neat holes blasted through the middle.

Today’s geothermal drill rigs can do the same, but they’re massive

While Dig’s prototype isn’t ready for commercial use, what I saw was substantially smaller than widely used geothermal drill rigs. The holes it drills are also straighter than those made

When it’s ready for its first commercial pilots — something this seed round will help accomplish — Dig’s rig will grow in size slightly, but it won’t require the large, double-axle trucks that currently dominate the industry.

The company is planning to sell the devices to drillers, giving them another option for existing projects and potentially opening avenues to new ones. Other companies are exploring the technology, too. 

“We shouldn’t have to require people to buy a $2 million rig, it should be something that’s lower cost where they can get into the business,” Madden said. “Geothermal should be in 100% of buildings. It’s in 1% of buildings. So how do we close the 99%?” she added. “It’s effectively an untapped market.”

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Tim De Chant Senior

Tim De Chant is a senior climate

De Chant is also a lecturer in MIT’s Graduate Program in Science Writing, and he was awarded a Knight Science Journalism Fellowship at MIT in 2018, during which time he studied climate technologies and explored new business models for journalism. He received his PhD in environmental science, policy, and management from the University of California, Berkeley, and his BA degree in environmental studies, English, and biology from St. Olaf College.

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