Geothermal (ground-source) heat pumps

An air-source heat pump exchanges heat with outdoor air, so its output falls as the air gets colder. A ground-source unit exchanges with the ground, which stays at a far more stable temperature, so its capacity does not collapse on the coldest day. The cost of that stability is the ground loop.

It depends on the loop type. A horizontal loop needs substantial open area that can be excavated; a vertical loop needs drilling access but far less surface; a pond loop needs suitable water. Shallow soil over ledge, which is common in parts of this area, pushes toward vertical and raises the cost.

It depends heavily on the site and how long you will own the building. Air-source equipment is far cheaper to install and has improved substantially in cold weather. Ground-source costs more upfront and delivers more stable output. For most existing homes here the air-source case is stronger. Geothermal makes most sense on new construction or larger properties with land.

Sometimes. Ground-source units can be configured for ducted air or hydronic output, but as with air-to-water systems the question is whether existing radiation can deliver enough heat at the water temperature produced. That is a calculation for your specific rooms.

Efficiency Vermont and the electric utilities publish their own figures for geothermal, and they differ from the air-source amounts. The federal Energy Efficient Home Improvement Credit is not available for property placed in service now. Check current amounts at the source before relying on any number in a proposal.

Substantially, and that is the honest answer. A horizontal loop means excavating a large area. A vertical loop means drilling. Both are best done before landscaping matters or as part of larger works, which is why new construction is the strongest case.

In residential use they mean the same thing, and ground source is the more accurate term. True geothermal energy means tapping the earth's internal heat: volcanic and deep geological sources used for power generation. A residential geothermal heat pump does something quite different: it exchanges heat with the shallow ground, which stays at roughly the average annual air temperature year-round because of solar gain and thermal mass, not because of heat from the earth's core. That stable temperature is what makes it more efficient than air source, since it never has to work against a minus-ten-degree day.

It comes down to land, geology and money. Horizontal loops need substantial open area that can be excavated. Vertical boreholes need drilling access and suitable geology, and Vermont's shallow ledge cuts both ways: it makes trenching hard and drilling normal. A pond loop is an option on some properties. Then the honest financial question: geothermal's installed cost is high, and in Vermont, cold-climate air-source heat pumps have become good enough and cheap enough that geothermal has to justify a large premium. It often does on a large or high-load building and often does not on a small one.

Realistically none of it. The ground loop requires drilling or excavation equipment, the loop must be purged and pressure-tested, the heat pump involves refrigerant work requiring certification, and Vermont regulates well drilling: a vertical borehole is drilled by a licensed driller. The homeowner's real contribution is at the front: getting the heat loss calculated properly, getting the loop sized to it, not to a rule of thumb, and comparing bids on the loop design rather than only on the equipment.

The ground around the loop gradually cools over the heating season and the system's performance degrades: worst in late winter, exactly when it is needed. Over years, an undersized loop in a heating-dominated climate like Vermont's can suffer long-term thermal drift, since the ground is being drawn down each winter faster than it recovers each summer. This is the defining risk of geothermal, it is invisible in the first year, and it cannot be fixed later without drilling more, which is the most expensive part of the system.

Installation is commonly one to three weeks, dominated by the loop field, drilling and grouting boreholes or excavating horizontal trenches, with the indoor equipment a few days at the end. Lifespan is the technology's strongest argument: the ground loop is generally expected to last fifty years or more, while the heat pump itself is typically twenty to twenty-five, considerably longer than an air-source unit because it lives indoors and never sees weather or defrost cycling.

Yes. More than one authority is typically involved. Vertical closed loops involve licensed well drilling and state requirements around borehole construction and grouting, designed to protect groundwater; local permits apply to the excavation and the mechanical work; and there may be requirements around loop fluid. Open-loop systems that draw and discharge groundwater face additional scrutiny. Confirm the current requirements with the Vermont Department of Environmental Conservation and your town before design, because these determine what is feasible on your site.

The ground loop is typically warrantied separately from the heat pump, loop piping for 25 to 50 years, the heat pump unit for a much shorter term more like a conventional heat pump, so a single 'geothermal warranty' figure usually understates or overstates what is actually covered depending on which part failed.

Sizing it to a rule of thumb instead of to a proper heat-loss calculation. An undersized loop degrades gradually over years as the ground around it fails to fully recover each summer, and by the time performance loss is obvious, the fix means drilling more: the most expensive part of the system to redo.