Is Geothermal Worth It? The Variables That Decide the Answer for Your House

Whether a ground-source heat pump is worth the money is a question about one specific house, not about geothermal in general. The technology works the same way in Vermont and in Arizona, but the economics turn on things that vary from address to address: what you are burning now, what your utility charges, what a driller finds under your yard, and how many winters you plan to spend in the building.

The published federal sources agree on the physics and the equipment. What they do not provide is a number you can apply to your own project. There is no authoritative nationwide figure for what a residential geothermal system costs installed today, and no federal agency publishes a payback table broken out by the fuel you would be replacing.

The economics turn on the variables below, each with the published figure behind it, its vintage, and its scope. House-specific values for them are what let you estimate whether the project pays back.

Why There Is No National Answer

The Department of Energy's Consumer Guide to Geothermal Heat Pumps, published in August 2021, says an average geothermal heat pump system costs about $2,500 per ton of capacity, roughly $7,500 for a three-ton unit. That figure is equipment only. DOE states it plainly: the $7,500 is before installation and drilling costs. Treating it as an installed price will understate a real project by a wide margin.

The National Renewable Energy Laboratory published per-ton figures that are labeled installed cost, $2,500 to $8,000 per ton depending on loop configuration and how mature the local market is. Those come from a June 2015 document titled Army Net Zero: Guide to Renewable Energy Conservation Investment Program (ECIP) Projects: a military energy-project planning guide, more than a decade old, not a database of residential bids. NREL does not clearly state the price year or the full list of exclusions.

So the two most-cited federal cost figures are an equipment-only price from 2021 and a military planning benchmark from 2015. Neither answers what the finished job costs on your street this year.

The same gap exists on the savings side. No federal source reviewed here publishes a residential comparison of geothermal against natural gas, propane, oil, electric resistance, or a modern air-source heat pump, fuel by fuel, with a payback period attached. The ENERGY STAR and DOE Federal Energy Management Program savings figures both compare efficient geothermal equipment against less efficient geothermal equipment.

Variable 1: The Fuel You Are Replacing

A heat pump does not create heat, it moves it, so its value is measured against the cost of the heat you stop buying. The higher the cost per delivered unit of heat from your current system, the more a geothermal system saves each year. That is why replacing electric resistance heat, propane, or fuel oil tends to be the more favorable case, and competing against inexpensive natural gas or an efficient air-source heat pump that already works tends to be the harder one. The direction follows from the cost of the displaced heat; the federal sources reviewed here do not publish a fuel-by-fuel ranking, so the size of the gap is a question for your own bills.

The direction of that effect is well established. The dollar amount is not: no verified authoritative fuel-by-fuel residential comparison exists in the federal sources reviewed, and current state-by-state residential prices for propane, heating oil, and natural gas are not something we can hand you here. Your own delivered fuel prices come off your own bills.

DOE's 2021 guide offers one equipment-level benchmark for the closest competitor: about $4,000 for a comparable air-source heat pump system with air conditioning, against $7,500 for a three-ton geothermal heat pump before installation and drilling. That is equipment cost only, and the installation gap widens considerably once a loop field enters the picture. For the full comparison between the two technologies, the ground-source versus air-source breakdown goes deeper. For the gas case specifically, see geothermal versus natural gas.

Variable 2: What You Pay for Electricity

Geothermal converts a heating bill into an electric bill. That trade is good or bad depending entirely on your rate.

The EIA figure worth having in front of you is the residential one. In 2025, the U.S. annual average residential retail electricity price was 17.30¢ per kilowatt-hour. The figure often used instead is 13.63¢. EIA's own sentence reads: "In 2025, the U.S. annual average retail price of electricity was about 13.63¢ per kilowatthour (kWh)." That is the all-sector average, blending residential with commercial at 13.41¢, transportation at 13.83¢, and industrial at 8.62¢, which pulls the blend down. Substituting 13.63¢ for the 17.30¢ residential average understates that national input by roughly a quarter. The figure that actually matters for any one household is the rate on its own bill.

National averages are a starting point and nothing more. Across all customer classes, EIA reports state averages from 8.20¢ per kWh in North Dakota to 35.72¢ per kWh in Hawaii. A factor-of-four spread in the input makes the operating-cost side of your analysis a local question. Use the rate on your own bill, including any time-of-use structure and any heat-pump tariff your utility offers.

Variable 3: Your Actual Heating and Cooling Load

A larger annual heating and cooling load creates more opportunity for operating savings to offset the installation premium. A large annual heating and cooling load gives it more hours to work with, which is why a high-load house may recover the premium considerably faster than a smaller, tighter house in a mild climate running comparable equipment.

Climate alone will not tell you this. House size, envelope tightness, window area, thermostat behavior, and system sizing all determine what your load actually is. A Manual J load calculation from a contractor, not a rule of thumb about square footage, belongs in this line of your analysis.

DOE's Federal Energy Management Program publishes regional lifecycle examples showing how strongly region and operating hours drive the arithmetic. In its 15-year analyses, the allowable efficiency premium came out to $2,162 in the Southeast, $842 in the Southwest, and $1,666 in Northern states. These figures need careful reading: they are the maximum price premium you could pay for efficient geothermal equipment over less-efficient geothermal equipment and still come out ahead. Not savings, and not a comparison of geothermal against any other technology. FEMP's phrasing for the Northern figure is that the required ENERGY STAR-qualified geothermal heat pump saves money if priced no more than $1,666 (in 2023 dollars) above the less efficient model.

Those examples assume a 36,000-Btu/h unit, electricity at 11¢ per kWh, a 3% discount rate, and region-specific operating hours. The 11¢ assumption sits well below the 17.30¢ residential average, worth noting before importing the conclusions into a household budget.

Improving the envelope first may cut the required tonnage and loop length, but it cuts both ways here. Air sealing, insulation, and duct sealing can reduce the tonnage and loop length you need, lowering the install price. They also reduce the annual savings available to repay whatever premium remains. No geothermal-specific dollar figure quantifies the net result.

Variable 4: Your Lot, Your Geology, Your Loop

The ground loop has no equivalent in any other HVAC installation, and it is where the cost uncertainty concentrates.

Open land favors horizontal trenches, which DOE says require at least four feet of depth. A pond or lake can support a submerged coil, which DOE says should sit at least eight feet below the surface. A constrained lot, shallow soil over bedrock, difficult equipment access, or poor soil thermal properties can force vertical boreholes, meaning a drilling rig and a meaningfully different bid. Loop selection turns on available land, access, soil, bedrock and groundwater, which is the ground covered by horizontal versus vertical ground loops and by the site assessment in whether your property is suitable.

For relative cost, the only reviewed source with a per-ton table is NREL's June 2015 Army Net Zero guide. Its new-construction figures, given as mature-market versus immature-market costs per ton, are $3,500 / $7,500 for horizontal loops, $4,000 / $8,000 for vertical loops, and $2,500 / $5,000 for surface-water systems. The table credits its own sources as Goetzler et al. 2009, Rafferty 2008 and EIA 2007, so the underlying data is older than the 2015 guide carrying it. That is a planning benchmark from a military program, not current residential pricing, and it establishes nothing about what a particular driller in your county will charge this month.

Current installed-cost differences between horizontal and vertical residential loops are not published anywhere authoritative. For your property, that comparison comes from bids.

Variable 5: New Construction or Retrofit

Project timing can materially affect the installed price. On a new build or a gut renovation, excavation, mechanical room, and ductwork can be coordinated with everything else on site. On a finished house with mature landscaping, the same work is an addition to a completed property, with restoration costs attached.

NREL's 2015 guide quantifies how the money splits. Heat-pump equipment ran $2,500 to $5,500 per ton depending on size, fan type, and local market, with installation, including ductwork, making up the remainder of system capital cost. The split between exterior loop and interior mechanical work was reported at 50/50 to 35/65 in new construction, and 45/55 to 25/75 in retrofits. The retrofit ratios tilt further toward interior work, which is what happens when ducts, electrical, and mechanical space have to be reworked inside a finished house. Same caveats: 2015, military planning guide, price year unstated.

Variable 6: How Long You Stay

A geothermal system pays back in annual increments. Leave before enough have accumulated and you paid the premium while someone else collects the benefit, unless the sale price captures it.

DOE's 2021 guide gives a generalized 5 to 10 year recovery period for the additional cost over an air-source system. Treat it as a rough historical indication rather than a promise. DOE does not disclose a complete set of assumptions behind the range; the August 2021 guide predates the expiration of the federal residential credit, which changed the net cost of any project that would otherwise have qualified for it; and the range covers the premium over an air-source system specifically, not over a gas furnace.

The resale question has no answer we can give you. No authoritative national estimate exists for how much geothermal adds to residential resale value, and local appraisal practice and buyer awareness vary enormously. If your ownership horizon is short, the safe assumption is that you recover the benefit through bills, not through the sale. Our payback period guide works through the mechanics of that calculation.

Variable 7: How Long the Equipment and the Loop Last

Longevity is worth stating precisely, because two very different components get blurred together and the buried half of the system is the long-lived one.

DOE reports an average life expectancy of more than 20 years for the heat pump itself, and 25 to 50 years for the underground infrastructure. Those are separate claims about separate hardware. The indoor unit, with its compressor, pumps, and controls, is a serviceable appliance on a normal HVAC replacement cycle. The buried pipe is closer to a site improvement. On those figures a well-installed loop can carry its value through at least one later indoor-unit replacement, which a straight first-cost comparison misses. Our system lifespan guide unpacks the component-by-component picture.

NREL separately reports that closed loops using HDPE pipe are typically warrantied for 50 years, while open-loop concepts carry warranties similar to the heat pumps themselves, 20 to 25 years. Those are warranty terms, not measured service life. A 50-year warranty is a commercial commitment about pipe, not evidence that any particular loop field will still be transferring heat in 2076. NREL makes the distinction itself, telling energy managers to model on either a 25-year or a 50-year cycle.

One modeling point sits underneath all of this. DOE FEMP uses a 15-year equipment-life horizon in its regional lifecycle examples, while DOE's consumer guide cites 20-plus years for the same class of equipment. Not a contradiction: a reported service life and a chosen economic analysis period are different things. It is reason enough to distrust any payback figure whose analysis period is not stated.

Variable 8: The Federal §25D Credit Ended for Post-2025 Work

Calculations built on the former 30% federal residential credit do not apply to qualifying expenditures made after December 31, 2025.

The residential clean energy credit under IRC §25D was 30% for qualifying expenditures made in 2022 through 2025. The IRS Instructions for Form 5695 state the current position directly: "You can't claim residential clean energy credits for expenditures made after December 31, 2025."

If you are pricing a geothermal system in 2026, no 30% federal credit applies to it. A project whose full cost would have been credit-eligible would have netted out at 70% of sticker and now nets out at 100% — about 43% more capital to recover. Your own figure depends on how much of the job would actually have qualified. For a project whose expenditures fall after December 31, 2025, a payback calculation that still deducts the former §25D credit understates the capital that has to be recovered.

DOE's August 2021 consumer guide still says geothermal may be eligible for tax credits. That was accurate when written and is stale for expenditures after December 31, 2025, which is why the publication date on a source matters as much as the agency's name on it.

Variable 9: Local Incentives and the Cost of Money

With the federal credit off the table, state and utility programs carry more weight than they used to. DOE notes that many states and electric utilities offer rebates or other incentives for the purchase of ENERGY STAR-qualified products. A grant, a rebate, a subsidized loop, a favorable electric rate, or low-interest financing can each shorten a payback materially.

What no source provides is an amount. There is no nationwide incentive figure, and current amounts for any particular state or utility cannot be verified without your ZIP code and your utility. Eligibility typically turns on equipment specification, installer credentials, and installation date as well as location, and programs open and close on their own schedules. This is a phone call to your utility and a check of your state energy office.

Financing costs belong in the arithmetic, and leaving them out flatters a long-payback project. Interest on a loan, or the opportunity cost of capital you could have invested elsewhere, can erase the nominal savings even when total undiscounted utility savings exceed the premium. DOE FEMP's examples use a 3% discount rate over a 15-year analysis period, a federal-agency assumption rather than a household one. No nationally representative residential geothermal financing rate exists in the sources reviewed. Use your own quoted loan terms.

Variable 10: Design, Sizing, and Who Installs It

Two houses on the same street with identical equipment can produce different bills. Envelope, window area, occupancy and thermostat habits account for part of that, and design and workmanship account for the part you are buying when you choose an installer.

Oversizing raises capital cost and can reduce efficiency, humidity control, and equipment life. An undersized loop or unit pushes the system into auxiliary electric resistance heat on the coldest days, which is exactly the expensive heat geothermal was installed to avoid. DOE identifies peak-load assessment, soil thermal conductivity, ground-temperature stability, water quality, and loop sizing as critical design inputs. A defensible design documents how each of those inputs was measured, tested or calculated.

No universal dollar penalty or efficiency-loss percentage is published for getting this wrong. The variation is too installation-specific to average. Practically, that makes the quality of your contractor a financial variable rather than just a service-experience one, and a bid without a load calculation and a loop design behind it is not a bid you can evaluate. The installation cost guide covers what should appear on a legitimate proposal.

What the Published Numbers Do Not Say

The authoritative sources reviewed here leave several household-level questions unanswered. Here is what could not be verified in the authoritative sources.

Local bids, a load calculation, your utility bills, permit costs, incentive terms and financing quotes supply most of the project-specific inputs the national sources leave out. Without those project-specific inputs, a confident national payback figure rests on assumptions that may not describe the house being evaluated.

Working Out Your Own Answer

A preliminary comparison starts with six inputs you can gather yourself. A full lifecycle analysis needs more than this — replacement schedules, maintenance, and an escalation assumption — but these six get you to a usable first answer.

One: your current annual heating and cooling spend, by fuel. Twelve months of bills, with heating and cooling seasons separated if your fuels differ.

Two: your electricity rate, from your own bill. Not 17.30¢ unless that happens to be what you pay. Include any heat-pump tariff your utility offers.

Three: a real load calculation. A Manual J from a contractor. It sizes the equipment and the loop, and it determines both the price and the savings.

Four: at least two installed bids, each showing loop type, tonnage, ductwork scope, electrical work, permits, and restoration. With no authoritative national price in existence, your bids are the price data. Two or more also reveal local price variation, though NREL's June 2015 mature-versus-immature spread does not establish how wide that variation is in today's residential market.

Five: your realistic ownership horizon. Use a conservative estimate rather than the longest plausible one. If the answer is five years, weight the analysis accordingly and do not assume the sale recovers the difference, because no source establishes that it does.

Six: your financing terms, if you are borrowing, or a defensible opportunity cost if you are not.

Those six get you to the comparison, though it needs two more figures your bidder should supply: the projected annual consumption of the proposed geothermal system, and an installed price for the alternative you would otherwise buy. Then it is arithmetic — annual operating cost of the geothermal system against annual operating cost of the alternative, divided into the price difference between the two installed projects, adjusted for the cost of money and checked against how long you will actually be there. Run it twice, once replacing the indoor unit at year 20 while keeping the loop, and once replacing the whole alternative system on its own schedule. The second scenario is what puts a number on retaining the underground infrastructure through a later indoor-unit replacement.

The answer sorts along the lines the evidence supports. A high-load home currently heating with electric resistance, propane, or oil, on a lot where the loop goes in economically, owned by someone staying long enough to collect, is the case most likely to pay. A home competing against inexpensive natural gas or a functioning efficient air-source heat pump, where drilling is expensive, electricity is costly, or the stay is short, is the case least likely to pay. A house matching neither of those limiting cases sits somewhere in between, and only its own numbers, run on the six inputs above, will say where. If you are weighing the non-financial side too, the pros and cons overview and the disadvantages of geothermal energy cover what the cost analysis leaves out.