Shift Key with Robinson Meyer and Jesse Jenkins

The Startup Trying to Put Geothermal Heat Pumps in America’s Homes

18 snips

Oct 22, 2025

In this conversation with Dulcie Madden, founder and CEO of Dig Energy, listeners discover how her startup is revolutionizing geothermal heat pumps. Dulcie reveals the technology behind ground-source systems and discusses how Dig's small drilling rigs could slash installation costs by 80-90%. They explore the efficiency, energy savings, and market potential for geothermal solutions in various U.S. regions. The discussion also touches on policy incentives and the future of geothermal infrastructure, painting an optimistic picture for cleaner energy.

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INSIGHT

Stable Subsurface Temperatures Are A Hidden Asset

Ground temperatures below the frost line stay ~50–60°F year-round and provide a stable thermal resource.
Using that thermal blanket makes heat pumps much more efficient than air-source alternatives.

INSIGHT

High Upfront Cost Blocks Adoption

Ground-source heat pumps have stayed near ~1% market share because upfront drilling and installation costs are very high.
High capital costs, not lack of awareness, prevented scaling historically.

ADVICE

Slash Drilling Costs To Unlock Market

Reduce drilling cost to make geothermal economically comparable to gas or air-source heat pumps.
Target an 80–90% drilling-cost cut so payback appeals to typical property owners.

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Simply operating America’s buildings uses more than a third of the country’s energy. A major chunk of that is temperature control — keeping the indoors cool in the summer and warm in the winter. Heating eats into families’ budgets and burns a tremendous amount of fuel oil and natural gas. But what if we could heat and cool buildings more efficiently, cleanly, and cheaply?

On this week’s episode of Shift Key, Rob and Jesse talk to Dulcie Madden, the founder and CEO of Dig Energy, a New Hampshire-based startup that is trying to lower the cost of digging geothermal wells scaled to serve a single structure. Dig makes small rigs that can drill boreholes for ground source heat pumps — a technology that uses the bedrock’s ambient temperature to heat and cool homes and businesses while requiring unbelievably low amounts of energy. Once groundsource wells get built, they consume far less energy than gas furnaces, air conditioners, or even air-dependent heat pumps.

Shift Key is hosted by Robinson Meyer, the founding executive editor of Heatmap, and Jesse Jenkins, a professor of energy systems engineering at Princeton University. Jesse is an adviser to Dig Energy.

Mentioned:

Dig Energy

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

Princeton University’s Geo-Exchange System

Jesse’s downshift; Rob’s downshift.

This episode of Shift Key is sponsored by …

Hydrostor is building the future of energy with Advanced Compressed Air Energy Storage. Delivering clean, reliable power with 500-megawatt facilities sited on 100 acres, Hydrostor’s energy storage projects are transforming the grid and creating thousands of American jobs. Learn more at hydrostor.ca.

A warmer world is here. Now what? Listen to Shocked, from the University of Chicago’s Institute for Climate and Sustainable Growth, and hear journalist Amy Harder and economist Michael Greenstone share new ways of thinking about climate change and cutting-edge solutions. Find it here.

Music for Shift Key is by Adam Kromelow.

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