Air-source and ground-source heat pumps compared
An air-source heat pump draws heat from outdoor air and costs less to install, while a ground-source heat pump draws it from buried loops and runs more efficiently, especially in deep cold. Ground source usually costs a multiple of air source up front, so the better choice depends on your site, budget and how long you will stay.
How do the two types differ?
An air-source unit has an outdoor coil and fan that exchange heat with the air. A ground-source unit, sometimes called geothermal, circulates fluid through pipes buried in the ground, in a vertical borehole or a horizontal trench, and exchanges heat with the earth. Below a certain depth the ground stays near the average annual temperature, so the source does not get colder when the weather does.
The indoor equipment is similar for both, and either can deliver heat through ducts or water-based systems.
How do cost and efficiency compare?
Air source is the cheaper installation, since there is no drilling or excavation. Ground source is typically much more expensive up front, and prices depend on soil, drilling conditions and loop length. Efficiency favours the ground, because the source temperature is steady. An air-source unit loses capacity and efficiency as the outdoor temperature falls, as the cold climate heat pump guide explains, while a ground-source unit stays closer to its rating.
That lower running cost may or may not repay the higher purchase price. Work through the sums with your own energy rates, using the approach in the heat pump versus furnace comparison.
What land and site work does ground source need?
- Vertical loops need drilling access and a modest footprint but can be deep.
- Horizontal loops need a large open area and excavation.
- Rock, high water table and utilities change the price and feasibility.
- Landscaping, driveways and building footprints may limit options on small lots.
A site assessment by a qualified installer is the only way to know. Air source needs only a pad or wall mount and clearance for airflow, with snow and drainage considered, as covered in defrost and noise.
How long do they last?
The indoor and outdoor equipment of both types has a service life of roughly 15 to 20 years or so, with differences by model and care. The buried loop of a ground-source system is expected to last considerably longer than the equipment, often several decades, because it has no moving parts. A ground loop is therefore sometimes treated as long-lived infrastructure that can be reconnected to a new heat pump. Maintenance practices are listed in the maintenance checklist.
What did Drake Landing do with the ground?
Drake Landing used the ground differently. Instead of drawing heat from stable earth, it stored summer solar heat in 144 boreholes about 35 m deep, and drew it back in winter, as the borehole storage page describes. That is seasonal storage, a different job from a heat pump loop, though both rely on the ground's thermal mass and insulation. The project reached a 100 percent solar share in the 2015-16 heating season, but it was wound down from about 2020 and decommissioned from 2024, showing that long-lived ground infrastructure still needs working equipment above it.
How should you decide between them?
Start with the house, not the technology. If it is leaky or poorly insulated, fix that first, because it lowers the load for either type. Then compare lifetime cost: purchase price, running cost over 15 to 20 years, expected maintenance and any rebate. A short stay in the house favours the cheaper air-source unit; a long one can favour ground source.
Lot size, soil and local drilling costs often decide the matter in practice. Where a large heating load, expensive fuel and a suitable lot line up, ground source can make sense. In most other cases, a good cold-climate air-source unit is the practical choice. Whatever you choose, ask how current rebates treat each type, since support has differed.
Quick answers
Is a ground source heat pump worth the extra cost?
It can be, if you will stay long enough, have a suitable site and face high heating bills. The extra cost is often large, so get quotes and model the savings with your own rates.
Do ground source heat pumps work in very cold weather?
Yes, because the ground temperature changes little with the air. Their capacity and efficiency hold up better than air-source units in deep cold.
Is geothermal the same as a ground source heat pump?
For home heating, the terms are used interchangeably. Geothermal in this context means a ground-source heat pump, not volcanic or deep-earth power generation.