Ground-source heat pumps, which tap into the stable temperatures found hundreds of feet beneath the Earth’s surface, are a super-efficient way to heat and cool homes. They’re also quite expensive to install in existing houses.
There’s a pretty straightforward reason: It’s hard to drill in a residential neighborhood. Hiring contractors to fit rigs into tight single-family yards and drill boreholes in places where utility infrastructure crisscrosses underfoot is a lot more complicated and expensive than installing an air-source heat pump, fossil-gas furnace, or other standard, aboveground HVAC systems.
But what if you could bore hundreds of holes at a time across a patch of cleared land and then build heat pump–equipped houses on top of them? That should be a lot cheaper. In fact, it could make ground-source heat pumps about as cheap as traditional HVAC offerings in newly built homes.
On Wednesday, Google X spinout Dandelion Energy and major U.S. homebuilder Lennar unveiled a partnership that aims to prove that proposition. The companies have pledged to build ground-source geothermal into more than 1,500 new homes in Colorado over the next two years, starting with Lennar’s Ken-Caryl Ranch development in Littleton, Colorado.
The goal is simple, Kathy Hannun, Dandelion’s founder and president, told Canary Media: “Can you get the up-front cost to be lower than everything else? Because then you have no reason not to do it.”
Just being able to tackle hundreds of boreholes at a time should more than halve the drilling costs that burden existing home retrofits, she said. Large-project economies of scale and designing homes around the high-efficiency heating and cooling that Dandelion’s system provides will yield further cost reductions, she said.
And by eliminating the need for new gas pipelines and reducing the peak electricity demands on the power grid, subdivisions built on this model could save a bundle on utilities as well, she said. That’s a key benefit cited in a January report from the Department of Energy, which found that widespread adoption of ground-source heat pumps, also known as geothermal heat pumps, could cut hundreds of gigawatts of peak demand and tens of billions of dollars in grid costs over the coming decades.
That study also found ground-source heat pumps could make a big dent in residential energy consumption and carbon emissions, particularly in climates where they outperform air-source heat pumps during cold winter weather.
But as it stands, the technology is in no more than 1% of U.S. homes, the report found. For comparison, air-source heat pumps are now in about 13% of U.S. homes.
The chief barrier, once again, is the up-front expense. Dandelion has spent the past eight years working to bring down those costs through a combination of technology and business-model innovation, and has done more than 1,000 home retrofits in the U.S. Northeast, targeting homes with high heating costs, many of which use expensive fuel oil.
To break into larger volume deployments, Dandelion has shifted its focus to new construction over the past two years or so, Hannun said. That pivot has naturally included Lennar, an investor in Dandelion that now owns about 10% of the startup, she said.
Colorado’s push for geothermal energy
Lennar and Dandelion aren’t disclosing cost data for the homes they’re collaborating on in Colorado. But, Hannun said, “in a few markets, the up-front cost of geothermal today is less than conventional” heating.
That’s certainly the case in Colorado, where Gov. Jared Polis, a Democrat, has made geothermal energy, or “the heat beneath our feet,” as he’s dubbed it in various state and regional policy initiatives, a big part of the state’s broader decarbonization strategy.
Over the past few years, the state has passed legislation creating tax credits for heat pumps, including ground-source systems, and competitive grants for geothermal energy projects. It also passed a law in 2021 that spurred Xcel Energy, the state’s largest utility, to launch a Clean Heat Plan that will provide significant rebates to projects that improve energy efficiency and help customers switch from gas to electric heating.
“The rebates coming out of Xcel’s Clean Heat Plan played a really significant role in the ability of the Dandelion-Lennar investments to pan out,” said Will Toor, executive director of the Colorado Energy Office, which manages state energy programs.
The government and utility incentives will also lower costs for people who aren’t buying these homes, because geothermal heat pump systems reduce the need for other utility infrastructure, he noted.
