Air-to-water heat pumps: heating, costs and cooling
An air-to-water heat pump takes heat from outdoor air and uses it to heat water for radiators or underfloor heating and, through a cylinder, domestic hot water for the bathroom and kitchen.
- Complete with installation
- €4,988 to €13,500 and more
- Zelená domácnostiam II subsidy
- up to €4,000
- Best suited to
- underfloor heating or large radiators
Prices from seller and installer offers, before subsidy, checked 20 October 2026. All prices and what they include.
Which homes it suits
The outdoor unit draws in air and extracts heat from it, even in winter. Using electricity, the heat pump transfers that heat to water, which then circulates through the heating system. Unlike other types of heat pump, it needs no borehole or well, which is why it is the most common choice for family houses.
The cooler the water a house needs for heating, the less electricity the heat pump uses. It is therefore best suited to:
- a house with underfloor heating, which can be heated with water at around 35 °C,
- a house with large radiators, which can heat a room with cooler water,
- an insulated house with low heat losses.
It can also go into an older house with small radiators, but you need to check that the radiators can heat the rooms with lower-temperature water, or choose a heat pump designed for higher water temperatures. There is more detail in our article on heat pumps for older houses.
The output you need in kW comes from a calculation of the house's heat loss, not its floor area. Two houses with the same floor area can need very different outputs.
Winter output and water temperature
Manufacturers state output under test conditions. A7/W35 means 7 °C outdoors (A for air) and 35 °C heating water (W for water). COP tells you how many kWh of heat the heat pump delivers from 1 kWh of electricity under those conditions. The colder it is outside and the warmer the water the house needs, the lower both output and COP. We explain why in how a heat pump works.
An example using one model rated at 9 kW:
The table shows two things:
- Output falls in frost. At −7 °C, this heat pump delivered 7 kW instead of 9 kW, roughly 22% less. When choosing, look at the output at the lowest temperatures in your area, not the number in the model name.
- Warmer water costs more electricity. With 55 °C water, the COP was 3.03 instead of 4.55, roughly 33% lower. In frost with 55 °C water, it was only 2.13.
A single COP figure does not tell you what you will pay in a year. Seasonal SCOP comes closer, but it too applies to test conditions, not to your house. We explain how to estimate annual consumption in heat-pump electricity consumption.
Hot water and cooling
Hot water
The heat pump heats domestic hot water in a cylinder. Some systems have it built into the indoor unit; in others it is separate. The cylinder is not always included in the price: of the 11 offers we collected, some included it and others explicitly did not. When comparing quotations, ask about the cylinder and its volume.
Cooling
Some air-to-water heat pumps can cool in summer. The appliance's capability alone does not mean it will cool your house, though. Check:
- whether the chosen model is reversible and cooling is included in the quotation,
- whether the underfloor heating or emitters are suitable for cooling,
- how the dew point is managed: the water in the floor must not be so cold that moisture condenses on it (Uponor controls the water temperature according to the dew point for this reason),
- whether the pipes are insulated so that water does not condense on them.
Monobloc and split
Air-to-water heat pumps are sold in two constructions. This is not a different heat source; it is about where the refrigerant is (SIEA):
- Monobloc: the whole refrigerant circuit is in the outdoor unit. Only water pipes run into the house.
- Split: refrigerant flows between the outdoor and indoor units. The refrigerant circuit is installed by a company certified to work with refrigerants.
Among the installed offers we collected, 3 were monobloc and 3 were split; the others did not state the construction. We compare differences in price, installation and practical experience on the monobloc heat pump page.
Price and installation
In the offers we collected, a complete air-to-water heat pump with installation cost from €4,988 to €13,500 and more, before subsidy. Cheaper offers tend to exclude the cylinder or cover less work. Examples showing exactly what they include are on the heat-pump price page.
Zelená domácnostiam II subsidy
Up to €4,000: €400 for each kW of output, for at most 10 kW and at most half of eligible costs. You pay the full price yourself first; the subsidy is reimbursed only after installation and approval of the application.
Calculate the subsidy for my quotationInstalling the outdoor unit means sorting out:
- a position with free airflow and service access, according to the exact model's instructions,
- a concrete base or a wall bracket,
- a condensate drain that will not freeze in winter,
- an electrical supply and circuit breaker.
The Slovak Building Act does not require a building plan or notification for equipment producing heat from renewable sources up to 50 kW (Act 25/2025, section 18(5)(i)). Other regulations or local conditions, such as heritage protection, may still apply. Check with the building authority. We describe the whole process in heat-pump installation.
Common questions
Can it cool through the floor?
Yes, if the model supports it and the system is designed for it. The water in the floor must stay warmer than the dew point, otherwise moisture condenses on the floor. That requires humidity-based control and insulated pipes. A designer or installer can assess whether your house can handle it.
Does it have the same output in frost?
No. Output and COP fall as the outdoor temperature drops. The model in the table above delivered 22% less heat at −7 °C than at 7 °C. Ask for the output at the lowest design temperature in your area and at the water temperature your house needs.
What is the difference between a monobloc and a split?
In a monobloc, the whole refrigerant circuit is outdoors and water runs into the house. In a split, refrigerant flows between the outdoor and indoor units, so installation includes refrigerant work. The heat source is the same in both cases: outdoor air.
Comparing heat-pump types
- Air-to-air
- Heats and cools rooms through wall-mounted indoor units, like air conditioning. It does not heat water.
- Ground-source
- Extracts heat from the ground through a borehole or garden collector. Ground works make up a substantial part of the cost.
- Water-source
- Extracts heat from groundwater in wells. It needs enough suitable water and the relevant permissions.
Sources
Output and COP come from the manufacturer's technical data under test conditions, not from measurement in a real house. Prices come from public offers by sellers and installers; each one's source and date is listed on the heat-pump price page. We do not sell or install heat pumps, and manufacturers do not pay us to mention their models.