What Is a Ground Source Heat Pump? A Plain-English Guide

A ground source heat pump is a single electric machine that both heats and cools a building by moving heat between the house and the ground — not by burning any fuel, and — in the standard water-source design — not by putting refrigerant into the earth. If you've heard the term and want a straight answer to "what is this thing, is it the same as geothermal, and what does it cost," this guide is the plain-English version.

The whole idea rests on one fact about the ground under your feet. A few feet down, soil temperature stops swinging with the weather and settles near-constant all year. About 30 feet down, the U.S. Department of Energy puts most of the country between 50°F and 59°F; the EIA measures roughly 50–60°F even at about 10 feet. That's warmer than winter air and cooler than summer air. A ground source heat pump uses that stable ground as a place to pull heat from when it's cold and dump heat into when it's hot. Everything below is the detail of how it does that — and what it costs you.

What a Ground Source Heat Pump Is

A ground source heat pump — GSHP for short — has three parts working as one system:

1. A buried loop of pipe (the "ground loop") in your yard, filled with water or a water-antifreeze solution.
2. An indoor heat pump unit, usually in a basement or mechanical room, with its own sealed refrigerant circuit and a compressor.
3. A distribution system — ductwork with an air handler, or a hydronic (water-based) setup like radiant floors — that carries the conditioned heat through the house.

The reason it's a heat pump and not a furnace is that it doesn't make heat by combustion or by glowing resistance coils. It moves heat that already exists in the ground, the same basic trick your refrigerator uses to move heat out of the food compartment. That's why a small amount of electricity can move a large amount of heat — the source of its efficiency, which we put real numbers on below.

Is It the Same as "Geothermal"?

Yes. "Ground source heat pump" and "geothermal heating and cooling" name the same technology. The Department of Energy uses the terms interchangeably — its own page reads "Geothermal heat pumps (GHPs), also known as ground-source heat pumps (GSHPs)." The EIA, ENERGY STAR, and the industry body IGSHPA all treat them as the same thing. So if a contractor quotes you a "geothermal system" and a neighbor calls theirs a "ground source heat pump," they're talking about the same machine.

One distinction worth keeping straight: residential ground source heat pumps are not the same as geothermal power. Geothermal power plants tap deep, hot rock to make steam and generate electricity for the grid. A ground source heat pump doesn't generate electricity and doesn't need hot rock — it works off the mild, steady temperature of ordinary ground a few feet down, and it uses electricity rather than producing it. If you want the energy-source picture, see our guide to what geothermal energy is.

How It Actually Works

In a standard closed-loop, water-source system there are two separate fluid paths that don't mix:

• The buried loop carries water or a water-antifreeze solution. It circulates out into the ground and back.
• The indoor unit runs a separate, sealed refrigerant circuit with a compressor.

Heat crosses between those two fluids at a heat exchanger inside the indoor unit. Critically, in a water-source GSHP the refrigerant stays inside the unit — it does not flow out through the buried loop. (There is a minority design, direct-exchange or "DX," where buried copper tubing does carry refrigerant directly; it's the exception, not the rule, and it's rarely installed today.)

Heating mode: the loop fluid picks up low-grade heat from the ground and carries it indoors. At the heat exchanger it hands that heat to the refrigerant; the compressor concentrates it to a useful temperature; and the system delivers warm air through your ducts, or warm water through a hydronic system, depending on how the home is set up.

Cooling mode: a reversing valve (a four-way changeover valve) flips the cycle. Now the system pulls heat out of your house, hands it across the heat exchanger to the loop fluid, and the loop fluid carries it down into the ground, which acts as a heat sink. The EIA describes it plainly: "In summer, the process is reversed. The system pumps unwanted heat from inside buildings into the cooler ground."

The Loop Types

The "ground loop" is the buried part, and how it's installed depends on your land, your soil, and your budget. The DOE and PNNL describe four common configurations, with these primary-verified depths:

Most closed loops recirculate a sealed water-antifreeze solution in a buried plastic loop (a minority "direct-exchange" design instead circulates refrigerant through buried copper — the exception noted earlier). An open-loop system is different: it draws actual groundwater from a well, runs it through the heat pump, and returns it to the ground through a recharge well or surface discharge — so the loop fluid there is well water, not a sealed antifreeze mix. Open loops can be cheaper to install where you have abundant clean water, but they depend on water quality and local discharge rules. Horizontal loops are the low-cost choice when you have the yard space; vertical loops fit small lots but cost more to drill.

Which loop suits a given property is its own decision — our guides to horizontal vs. vertical loops and open vs. closed loops walk through the trade-offs in detail.

How Efficient It Really Is

Efficiency is where ground source heat pumps earn their keep, and it's also where the internet is full of bad math.

The primary numbers come from ENERGY STAR: a certified geothermal heat pump uses 61% less energy than a standard model, saves the typical household about $830 a year, and delivers more than $9,500 in savings over a 15-year life. ENERGY STAR also states these systems are more than 45% more energy-efficient than standard options.

The efficiency of a heat pump is measured by COP (coefficient of performance) in heating and EER in cooling. A COP of 3 to 5 means the system delivers 3 to 5 units of heat for every 1 unit of electricity it consumes — the DOE describes these systems as moving roughly three to five times the energy they use.

How Long It Lasts

A ground source heat pump splits into two lifespans, and this is one of its quiet advantages. The DOE's Building America program (PNNL) puts the indoor components at about 25 years and the buried ground loop at more than 50 years. The loop is the expensive, disruptive part to install — and it's the part that outlasts nearly everything else in the house. When the indoor unit eventually wears out, the loop stays in the ground and the replacement is a fraction of the original job.

For comparison, a conventional air conditioner or air-source heat pump sitting outside in the weather typically lasts on the order of 15 years. Keeping the heat-exchange loop underground, out of the sun and the freeze-thaw cycle, is a big part of why the geothermal equipment lasts as long as it does.

What It Costs

Here's where we're going to disappoint anyone hoping for a single tidy number — because there isn't one.

There is no current, all-in government price for a ground source heat pump install. An older DOE consumer guide cites roughly $2,500 per ton for the equipment — but it explicitly excludes the drilling and installation that dominate the real bill, so it isn't a usable total. The all-in ranges you see quoted around the web — commonly somewhere in the tens of thousands of dollars — come from third-party market aggregators, not from a federal source. They're real-world estimates, but they're wide, and they swing hard with your loop type, your soil, your local drilling costs, and your home's size. Treat any cost you read (including ours) as a market estimate to verify with local quotes, not a fixed price.

What is well-established is the operating-cost logic: because the system moves heat instead of burning fuel, it runs on far less energy than resistance heat or a conventional furnace-and-AC pairing. The defensible sourced figures are ENERGY STAR's — a certified geothermal heat pump uses 61% less energy than a standard model and saves the typical household ~$830/year.

Is One Right for Your Home?

A ground source heat pump makes the most sense when a few things line up:

• You have room for a loop. A yard big enough for horizontal trenches, or a lot where vertical drilling is feasible. Suitability is a real question — our guide to whether your property is suitable covers it.
• You're staying put. The high upfront cost pays back over years through low operating costs, so the longer you own the home, the better the math.
• You want one system for both seasons. A GSHP replaces both the furnace and the air conditioner, and it can preheat your hot water on the side.

It's a weaker fit if you're on cheap natural gas, moving soon, or working with a lot that can't accommodate a loop. It isn't right for everyone — the upfront cost is real, and it's the reason many good candidates still pass. If you're weighing it against a conventional air-source system, that head-to-head lives in our ground source vs. air source comparison.

Frequently Asked Questions

Is a ground source heat pump the same as geothermal? Yes. "Ground source heat pump" is the precise name; "geothermal heating and cooling" is the everyday name. The DOE uses both. It is not the same as geothermal power, which generates grid electricity from deep hot rock.

Does a ground source heat pump use electricity? Yes — it runs a compressor and a circulating pump. It's efficient because it moves far more heat than the electricity it consumes (a COP of 3–5), not because it uses no power.

How deep does the loop go? It depends on the type. Horizontal trenches run about 4 feet deep; vertical boreholes run roughly 100–400 feet deep and are spaced about 20 feet apart (PNNL). Pond loops sit at least 8 feet below the water surface.

How long does it last? The indoor unit lasts about 25 years and the buried ground loop more than 50 years (DOE/PNNL) — one reason the long-run economics work out.

Can it heat my water too? Often, yes — via a desuperheater that can supply roughly 25–50% of household hot water as a byproduct, most effectively in cooling-dominated climates (PNNL).