The Fundamental Question: Air or Ground as Heat Source?
Once you have decided on a heat pump, the next question is: which type is right for your home? The two most popular variants are the air-to-water heat pump and the ground-source heat pump (brine-to-water). Both have their strengths and weaknesses, and the right choice depends on your property, your budget, and your long-term goals.
Costs in Direct Comparison
The air-to-water heat pump is significantly cheaper to purchase. Including installation, you should expect 15,000 to 25,000 euros in 2026. There are no drilling costs, and installation is typically completed within 2 to 3 days. The ground-source heat pump costs 20,000 to 35,000 euros, with deep drilling (50 to 80 euros per drilling meter at typically 80 to 100 meters depth) making up the largest cost component.
When it comes to operating costs, the picture reverses: Thanks to the higher seasonal COP (3.5 to 4.5 versus 2.8 to 3.5), the ground-source heat pump uses 20 to 30 percent less electricity. With an electricity demand of 5,000 to 7,000 kWh per year, this saves 200 to 500 euros annually. Over a lifespan of 20 to 25 years, this adds up to 4,000 to 12,500 euros in operating cost savings.
Efficiency and Performance Throughout the Year
The greatest advantage of the ground-source heat pump is its consistent performance throughout the year. Below 10 meters depth, the ground maintains a constant temperature of approximately 10 degrees. This means the seasonal COP remains just as high in winter as in spring. The air-source heat pump, on the other hand, struggles on cold winter days: at minus 10 degrees outdoor temperature, performance can drop to 50 to 60 percent of rated capacity, and defrost cycles (to de-ice the evaporator) consume additional energy.
In practice, this means: on the coldest days of the year, when the most heat is needed, the air-source heat pump operates at its least efficient. Ground-source heat pumps do not have this problem. For regions with frequently harsh winters (Alpine foothills, mountain regions), ground-source is particularly recommended.
Space Requirements and Permits
The air-to-water heat pump only needs a placement spot for the outdoor unit, typically 1 by 1 meter on the house wall or in the garden. The minimum distance to neighbors (3 meters) must be observed due to noise emissions. Modern units at 35 to 45 decibels are significantly quieter than early models but not silent. A building permit is generally not required.
The ground-source heat pump requires either space for ground probe drilling (approximately 100 meters drilling depth per 10 kW heating load, distributed across 1 to 3 boreholes) or a large garden area for horizontal collectors (approximately 1.5 to 2 times the heated living area). Both require a water rights permit from the local water authority and potentially a mining notification for boreholes over 100 meters. The approval process takes 4 to 8 weeks.
Lifespan and Maintenance
Both types have an expected lifespan of 20 to 25 years for the compressor. The ground probes, however, have a lifespan of 50 to 100 years and outlast multiple heat pump generations. Maintenance costs are low for both types: an annual inspection for 150 to 250 euros. For air-source heat pumps, evaporator cleaning is added; for ground-source, the brine should be checked every 5 to 10 years.
Which Type Suits Your Home?
An air-to-water heat pump is better when: you have a lower budget, limited property space, want quick installation, are renting out the property, or plan to sell within 10 to 15 years. A ground-source heat pump is better when: you plan long-term use over 15 years, have sufficient property, live in a cold climate region, have high heating demand, and want maximum efficiency.
In both cases: Use our calculator to compare costs, subsidies, and payback periods for both variants. Simply change the heat pump type and compare the results. This way you make an informed decision.