A geothermal heat pump doesn’t tap into volcanic heat or anything from deep underground. It works because the ground a few feet down holds a steady temperature, somewhere between 40°F and 70°F depending on where you live, all year round, according to the Department of Energy. A loop of buried pipe carries fluid down into that stable zone and back up, and a heat pump inside the house uses it to pull warmth out in winter and dump heat back into the ground in summer. Installed systems for a typical single-family home run $15,000 to $40,000, according to EnergySage, though the number swings a lot based on the loop you choose and what’s under your yard.
The ground loop, not a volcano
Nothing about a residential geothermal system reaches magma or tectonic heat. That’s the geothermal power plants you hear about in Iceland or parts of California, where wells go down thousands of feet into genuinely hot rock. A home system, more accurately called a ground-source heat pump, runs off something far less dramatic: dirt and rock a handful of feet under the frost line stay close to the region’s average annual air temperature, whether it’s January or July.
A sealed loop of high-density plastic pipe, filled with water or a water-antifreeze mix, runs down into that zone and back up to a heat exchanger. In winter, fluid that’s cooler than the house but warmer than the outdoor air comes back up from the ground, and the heat pump concentrates that warmth and pushes it inside. In summer the process runs backward: heat gets pulled out of the house and dumped into the ground, which stays cooler than the summer air. Either direction, the compressor does far less work than an air-source unit fighting a 20°F night in January or a 95°F afternoon in August.
Four ways to bury the loop
How the loop gets installed depends mostly on how much land is available and what’s under it.
Horizontal loops get buried in trenches, usually four to six feet deep, and need enough open yard to run several hundred feet of pipe per ton of heating and cooling capacity. It’s the cheapest option when there’s room for it, per the Department of Energy.
Vertical loops go into boreholes drilled 100 to 400 feet down, spaced a set distance apart and connected at the bottom. They cost more per foot, since drilling is expensive, but they work on small lots where a horizontal trench field has no chance of fitting.
Pond or lake loops submerge coiled pipe in a body of water deep enough that it won’t freeze solid. Where a homeowner already has a pond of the right size and depth, this tends to be the least expensive loop to install, since there’s no trenching or drilling involved at all.
Open-loop systems pull groundwater from a well and run it through the heat exchanger before returning it to the aquifer through a second well or an approved discharge point. It can undercut a closed loop on price, but it only works where local water rights and groundwater quality allow it, and plenty of jurisdictions restrict or ban it outright.
How efficient these systems run
ENERGY STAR certifies closed-loop water-to-air geothermal systems at a coefficient of performance, or COP, of at least 3.6, and open-loop systems at 4.1 or higher. In plain terms, a COP of 3.6 means the system delivers 3.6 units of heat for every unit of electricity it consumes. Standard electric resistance heat, by definition, tops out at a COP of 1. A gas furnace, which burns fuel rather than moving existing heat, can’t beat that 1-to-1 ratio no matter how efficient it gets.
That gap explains why a ground-source system is worth the higher upfront cost. It moves three to four units of heat for every one it pays for in electricity, and it can do that because the ground it’s drawing from already sits closer to room temperature than the winter air does.
What installation costs
Carrier puts a typical whole-home installation at $10,000 to $30,000, with the full range running $12,000 to $45,000 once site conditions and system size get factored in. EnergySage’s number lands close, $15,000 to $40,000 or more, and it flags at least one real installation, in Massachusetts, that came in at $78,000.
What moves the price: vertical drilling costs more per foot than a horizontal trench, and rock underneath a lot costs more to drill through than soil. A larger home needs more tons of capacity, which means more pipe, deeper wells, or a bigger horizontal field. A retrofit into a house with old or undersized ductwork often needs that work done at the same time as the heat pump and loop. And a yard a drilling rig can’t reach easily adds cost before the first foot of pipe goes into the ground.
The federal tax credit is gone
As of this writing in 2026, the 30% federal tax credit for residential geothermal, known as Section 25D, no longer applies. The One Big Beautiful Bill Act, signed July 4, 2025, repealed both Section 25C, which covered efficiency upgrades including air-source heat pumps, and Section 25D, which covered geothermal, effective for anything not placed in service by December 31, 2025. IRS guidance is specific on that cutoff: the credit “is not available for any property placed in service after December 31, 2025,” and placed in service means operational, not merely paid for or under contract.
Homeowners who got a geothermal system running before the end of 2025 can still claim the 30% credit on Form 5695 with their 2025 return. Anyone installing one now pays full price at the federal level. The law did carve out one workaround for the industry: commercial-grade geothermal systems are now exempt from a rule that used to block leasing them to homeowners, so some installers are shifting toward leased systems rather than owned ones with a credit attached. What’s left federally are the HEAR and HOMES rebate programs, which pay out based on income or measured energy savings and are rolling out state by state through 2026, on top of whatever your own state runs. The DSIRE database tracks those state and utility programs if you want to check what’s still on offer where you live.
Payback, and what moves it
The Department of Energy says payback runs about 5 to 10 years in energy savings, though EnergySage’s version of the same DOE guidance puts it closer to 10 to 15 years. Either estimate can be right, depending on the house.
What fuel you’re replacing matters most. Swapping out propane or heating oil, both expensive per unit of heat, pays back faster than swapping out cheap natural gas. Your local electricity rate matters too, since the system’s entire operating cost is electric. A long, cold heating season with real summer cooling load runs the loop harder and pays it off faster than a mild climate that barely needs either. And with the federal credit gone, every project now takes meaningfully longer to break even than it would have with the 30% credit knocking a third off the upfront cost.
When an air-source heat pump is the better call
Ground-source systems aren’t the right answer for every house. A standard air-source heat pump installed whole-home runs an average of $15,393 before incentives, according to EnergySage, with a national range from around $8,000 in New Mexico to $33,000 in New York. The equipment is no bigger than a central air conditioner and a furnace, and there’s no loop field to size against the shape of your lot.
Cold-climate air-source units have also closed a lot of the performance gap. A Northeast Energy Efficiency Partnerships study cited by the Department of Energy found cold-climate heat pumps in the Northeast saved around 3,000 kWh a year, worth about $459, compared with electric resistance heat, and 6,200 kWh, worth about $948, compared with oil heat.
From the sales side, the easiest geothermal sale is a homeowner who’s already burning propane or oil and has either the yard for a horizontal loop or the budget for vertical drilling. Add a plan to stay in the house long enough to see the payback through, and it’s an easy case to make. Take away any one of those conditions and an air-source heat pump usually wins. A small urban lot without room for a loop field forecloses geothermal on its own. A house on a slab that needs new ductwork either way erases part of geothermal’s advantage. And an owner who might sell in five years won’t be the one collecting a fifteen-year payback.
Ground-source systems still make sense where the site and the timeline both cooperate. They don’t clear that bar as often now that the tax credit that used to close the gap is gone.
