Geothermal heat pumps: what the ground loop costs and what it buys

Updated September 14, 2026 · Claude AC · 3 sources cited

Contents (7)

The loop is the variable
Where the money goes
What you get for it
The federal credit has ended — read this carefully
Does it repay? It depends entirely on what it replaces
When the answer is no
Frequently asked questions

Every geothermal quote is really two quotes stapled together. One is for a heat pump — a box in the basement or the utility room, not unlike the air-source equipment sitting outside your neighbour’s house. The other is for a hole in the ground, or several, and that second number is why two homeowners in the same county can be quoted amounts that differ by a factor of two for identical equipment.

Understanding which half of the bid is which is the only way to read a geothermal proposal, because the machine is a commodity and the loop is a construction project.

The loop is the variable

A ground-source heat pump exchanges heat with the earth instead of the air, using water or an antifreeze mix circulated through buried pipe. Below a few metres the ground holds close to the local annual average temperature year-round — cooler than August air, far warmer than a January night — and that stability is the entire proposition. How you reach it is the cost question.

Loop type	What it needs	Relative cost	The catch
Horizontal, trenched	Open land and machine access — typically a significant area of yard	Lowest, where land exists	Landscaping, mature trees and septic fields are in the way; shallower pipe is more affected by seasonal swing
Vertical boreholes	A drill rig on site, boreholes hundreds of feet deep	Highest, and the most site-dependent	Geology decides the price — rock, sand and water table all change the day rate
Pond or lake loop	A body of water of adequate depth and volume that you control	Low when available	Rarely available; permitting and depth requirements are real
Open loop (well water)	A productive well plus a legal discharge route	Low capital, higher long-term risk	Water chemistry fouls heat exchangers; discharge is regulated locally and pumping is a running cost

All figures in this guide are ranges of what households report, not quotations. Anyone who gives you a national price for a geothermal installation without asking about your soil, your acreage and your ductwork is quoting a number they cannot honour.

Where the money goes

Treat a proposal as four lines, and ask for them separately:

The heat pump itself, plus a desuperheater if you are taking one for domestic hot water. Comparable in order of magnitude to a high-end air-source system.
The ground loop — drilling or trenching, pipe, grout, header, and restoring the yard afterwards. On a vertical installation this is frequently the largest single line and the one that varies most.
The interior work — circulating pumps, buffer or flow centre, electrical, and whatever the ductwork needs. Reusing sound existing ducts saves a great deal; discovering they are undersized for the airflow a heat pump wants does the opposite.
Design and commissioning — the loop must be sized to the calculated load, and the system flow-tested and documented. This is not a line to compete away.

The total for a whole-house retrofit typically lands well above a conventional system replacement, often by a multiple rather than a percentage. New construction is a different economy: the excavator is already on site, the ducts are being designed anyway, and the incremental cost over a high-efficiency conventional system is far smaller.

What you get for it

Efficiency is rated differently from air-source equipment — geothermal units are tested to water-loop conditions rather than the outdoor-air conditions behind SEER2, so the numbers are not directly comparable. The physical advantage, though, is easy to state: the source temperature barely moves. There is no defrost cycle in January, no capacity collapse when the air hits 5 °F, and no backup resistance heat quietly running up the bill — the failure mode dissected in our guide to cold-climate heat pump performance. In summer the same stability means the unit is rejecting heat into ground that is cooler than the afternoon air, exactly when an air-source condenser is struggling.

Two secondary benefits are underrated. There is no equipment outdoors, so nothing to be hailed on, stolen, hit by a mower or heard by a neighbour. And the buried loop is a very long-lived asset: high-density polyethylene pipe, fusion-welded and buried, is generally expected to outlast the heat pump it serves several times over, while the machine itself is on a life comparable to other residential HVAC equipment.

The federal credit has ended — read this carefully

For years the arithmetic of residential geothermal rested on the Section 25D Residential Clean Energy Credit, worth 30 percent of the cost with no dollar cap. That is over. The IRS states that the credit applies to qualified property installed from 2022 through 31 December 2025, and that it is not available for any property placed in service after 31 December 2025. There is no phase-down and no grace period for residential work.

The practical consequences for anyone pricing a system in 2026:

Any quote that still shows a 30 percent federal line for a home installation is either out of date or misleading. Ask for it to be removed and look at the real number.
If your system was placed in service during 2025, the credit is claimable on that year’s return — a matter for your tax preparer, not your contractor.
The separate Section 25C credit for efficiency improvements also terminated at the end of 2025; our guide to HVAC tax credits and rebates covers what that changes.
State, utility and co-op programmes are now the incentive layer that matters, and they vary enormously. Check your own utility rather than a national summary, and check whether a special electric rate for heat pump customers exists — over twenty years that tariff can be worth more than any one-time rebate.

Rules for rental and commercial property sit under different sections of the code with their own timelines; that is a question for a tax professional, not a cooling guide.

Does it repay? It depends entirely on what it replaces

The payback on geothermal is not decided by the geothermal system. It is decided by the fuel you stop buying.

What you heat with today	How the case looks now the credit is gone
Propane or fuel oil	The strongest case. High delivered-fuel cost against a machine drawing heat from the ground; the annual saving is large enough to carry a big capital cost
Electric resistance — baseboards or strips	Very strong, particularly in a cold climate where an air-source unit would lean on backup heat
Cheap natural gas	Hardest. The gas bill being displaced is small, so the payback stretches beyond most owners’ horizon
An existing air-source heat pump	Marginal on energy alone. The gain is real but incremental — it is a comfort and longevity argument
Cooling only, mild winters	Rarely justifiable. You are paying for a loop to solve a heating problem you do not have

When the answer is no

Geothermal is a poor fit if you have no drillable or diggable land, if you expect to move within a few years, or if the load is modest and a couple of well-placed heads would do — the comparison in our guide to mini-splits versus central air and the wider heat pump section is the honest starting point for most households. It is also a poor fit where no local contractor has a real track record: this is a trade where loop design errors are buried in the yard and expensive to reach. Ask for addresses of installations that have been through several winters, and ask what the loop was sized from.

Frequently asked questions

Is the 30 percent federal tax credit for geothermal still available?

Not for residential installations completed from 2026 onward. The IRS is explicit that the Residential Clean Energy Credit is not available for property placed in service after 31 December 2025. Systems placed in service during 2025 remain claimable on the relevant return. Treat any 2026 quote showing that credit as a red flag.

How much land does a ground loop need?

It depends on the loop type far more than on the house. A horizontal loop needs a meaningful area of open, machine-accessible ground clear of septic fields, wells, trees and utilities. Vertical boreholes need only a small footprint but require rig access, and they are the reason geothermal remains possible on suburban lots. A site survey answers this in a way that no rule of thumb can.

How long does a geothermal system last?

The two halves age very differently. The buried polyethylene loop is expected to last for decades beyond the equipment and is normally reused when the heat pump is replaced — which is the quiet long-term argument for the technology. The heat pump itself has a service life broadly comparable to other residential HVAC equipment, helped by living indoors rather than in the weather.

Does a geothermal heat pump work for cooling as well?

Yes, and it is one of its better arguments. In cooling it dumps heat into ground that is well below afternoon air temperature, so it does not lose capacity on the hottest day the way an air-cooled condenser does — the effect described in our guide on an air conditioner that cannot keep up in a heat wave.

Can an existing duct system be reused?

Sometimes, and it matters to the budget. Heat pumps generally move more air at a lower supply temperature than a furnace, so ducts sized tightly for a hot-air system can be undersized for the job. A static pressure measurement during the survey, not a glance in the basement, is what settles it.