Yes, many heat pumps can cool – but as gentle temperature control via the underfloor heating, not as air conditioning. Geothermal probe systems cool «passively» almost at zero cost, air-water devices need the reversible version for this. The limit is not set by the heat pump, but by the distribution system: radiators cannot cool, and the dew point sets a limit for the cold water temperature. (As of: July 2026)
Key points in brief
- Two types: passive cooling or «free-cooling» (only with geothermal probe – the cool comes directly from the ground, almost without electricity) and active cooling (reversible devices reverse the circuit).
- The realistic expectation is temperature control: a few degrees cooler and noticeably more pleasant – not the air conditioning feeling of 21 degrees in the heat outside.
- Cooling takes place via surfaces, almost always the underfloor heating; radiators are ruled out, and the dew point limits how cold the water may be (condensation!).
- Summer supplies the electricity at the same time: Active cooling runs precisely when your own solar system produces the most.
- Anyone planning a heat pump today clarifies the cooling function now – retrofitting is complex to impossible depending on the system.
Can a heat pump cool at all?
Technically, it makes sense: A heat pump is essentially a refrigeration circuit – the same as in a refrigerator – which pumps heat from A to B. In winter, it brings heat from outside into the house; in principle, there is nothing against reversing the direction in summer and extracting heat from the house. This is exactly what cooling-capable heat pumps do – in two very different ways, and the difference is the core of this guide.
Important first of all: Not every heat pump can do it. The cooling function is a question of equipment – for the device, the hydraulics and the control system. Anyone who wants it or would like to keep the option open says so in the planning meeting, not after commissioning.
Passive cooling: the silent trump card of the geothermal probe
Here the brine-water heat pump plays its elegant special trump card: The ground is significantly cooler than the living spaces in summer. With passive cooling (also «free-cooling»), the brine circulates through the geothermal probe and takes the room heat into the ground via a heat exchanger – the compressor, the energy-hungry heart of the heat pump, remains off. Only circulation pumps and control systems run: Cooling almost at zero cost.
The side effect is remarkable: The introduced summer heat regenerates the geothermal probe – the ground from which the winter extracted heat gets a part back. Passive cooling is thus one of the rare cases where comfort does not burden the system, but cares for it. Anyone planning a geothermal probe should seriously plan for passive cooling – the additional effort during construction is manageable, retrospectively it becomes more complex.
Active cooling: the reversed heat pump
Air-water heat pumps do not have a cool ground at hand – they cool actively: A reversible device reverses the refrigeration circuit and pushes the room heat outside, exactly the air conditioning principle. This works, but costs electricity, because the compressor is now running.
Here the summer helps the bill: Active cooling is needed exactly when your own solar system delivers the most – heat days are yield days. Anyone who has PV on the roof cools largely with their own surplus on critical afternoons; cooling becomes an additional self-consumption lever instead of a cost item. Without your own roof, it remains a conscious comfort decision with running costs.
The actual limit: the distribution system and the dew point
The heat pump could often do more than the house can handle – because cooling takes place via the same surfaces via which heating takes place, and there are two hard rules here:
Radiators cannot cool. Their small surface area is no good for cold water – before a radiator noticeably cools a room, it mists up like a cold glass in summer. Surface systems are cooling-capable: above all the underfloor heating, in principle also ceiling or wall surfaces. Anyone who only has radiators will realistically not cool via the existing radiators – there is a second way for this, which is almost always forgotten in conversation.
The exception for radiator houses: Fan coils. A fan coil does not guide the cold water over a large static surface, but through a small heat exchanger over which a fan blows room air. This solves both problems of the radiator at once: The effect comes from air movement instead of from the surface, and because the device has a condensate tray with a drain, moisture is not a damage case, but planned in – the convector may therefore run colder than a floor. The price for this is exactly what makes surface cooling so pleasant: Air moves, and you hear the device. Furthermore, every room needs its own device including a condensate line, which makes retrofitting a construction task. For individual critical rooms – the bedroom, the office under the roof – it is nevertheless often the only solution that works together with the existing heat pump instead of running alongside it. The prerequisite remains that the system can deliver cold water at all.
The dew point sets the limit. If a surface becomes colder than the dew point of the room air, moisture condenses – the misted floor is not only unpleasant, but moisture damage waiting to happen. Therefore, cooling-capable systems regulate the cold water temperature conservatively and monitor the humidity (dew point monitor). The consequence for expectations: Surface cooling provides temperature control. It takes the oppressive peak off a room – a few degrees, evenly and draft-free –, but it does not create the cold air conditioning feeling. Anyone who wants 21 degrees at an outside temperature of 35 degrees needs another device and should have it quoted as such.
This very gentleness is incidentally the comfort advantage: no drafts, no noise in the room, no dry air – the floor is simply pleasantly cool instead of warm to the feet.
Heat pump as air conditioning – where the comparison holds up and where it falls down
The question almost always comes in exactly these words: Can the heat pump replace the air conditioning? The technical relationship is close – a reversible device works on the same principle as an air conditioning unit, it just distributes the cold differently. And the answer is decided by this distribution.
The difference lies less in the cold itself than in the pace and the air. An air conditioning unit works in minutes and dehumidifies at the same time – hence the immediate effect, and hence also the drier air afterwards. Surface cooling works the other way around: over hours, without air movement, with the dew point limit from the previous chapter as a hard cap. Anyone who knows this asks the more useful question – not «does it cool?», but «is this kind of cooling enough for me?».
The honest summary: As basic temperature control of a well-shaded house, the cooling function actually replaces the air conditioning unit in many cases – you simply do not miss it. As an emergency device for the heated attic, it does not replace it. Anyone who needs both combines sensibly: surface cooling as a quiet base load for the entire house, a fan coil or a split device for the one room that needs it.
Retrofitting free-cooling: What works and what doesn't
The most frequent question after the first hot summer is: «Can I have this retrofitted?» The answer depends on the heat source system – and it turns out oppositely for the two designs.
With existing geothermal probe: often feasible, but not a quick fix. Free-cooling needs a heat exchanger between the brine and heating circuit, changeover valves, a dew point monitor and a control system that knows summer operation. Some manufacturers offer a retrofit module for this, with other devices it becomes a custom-made item in the boiler room. Whether it is possible is decided on three points: Can the brine circuit be tapped cleanly, is there space in the boiler room, and can the existing control system map the cooling operation at all? The specialist company clarifies this on site – the effort is noticeably higher than what the same function would have cost when the system was built new.
With air-water heat pump: not in this form. Free-cooling relies on the heat source being cooler than the house in summer. This is the case with the ground, but precisely not with the outside air in midsummer – the approach falls away physically. What works with air-water devices is active cooling with a reversible refrigeration circuit. And this reversibility is a characteristic of the device: A non-reversible device cannot be made into one retrospectively. The honest consequence for everyone planning an air-water heat pump today and unsure about cooling: The option costs little at purchase and is no longer available at all later on.
In both cases, the condition from the previous chapter remains – without surface heating, the best cooling function is useless. Anyone who only has radiators is better off checking the fan coil variant straight away instead of the free-cooling retrofit.
For businesses where not the house, but a cold room is cooled, a different logic applies: There the refrigeration system is the biggest electricity consumer – and the solar system the suitable partner, because cooling load and yield coincide in time. More on this in the article Solar system for cold store and cold storage.
What does this mean for planning and everyday life?
During new construction or heating replacement: Lodge the desire for cooling early on. With the geothermal probe, this means planning in passive cooling, with air-water choosing a reversible device – and in both cases installing the hydraulics (changeover, dew point monitoring) right away. The surcharge in the project is moderate; retrofitting to an unprepared system is not.
In operation: Surface cooling works like surface heating – slowly and continuously. It is not switched on in the midday heat, but runs quietly throughout the hot spell; ideally combined with classic summer behaviour (ventilating at night, shading during the day), which it supplements rather than replaces. And it is no substitute for shading: no floor can fight against a roof window without blinds.
The honest priority: Cooling is the bonus of the heat pump, not the reason to buy it. It is dimensioned based on the heating demand; the cooling function is the addition that extracts additional comfort in summer from the same technology – almost free of charge with the geothermal probe, with air-to-water at the price of electricity, which in the best case is supplied by your own roof.
The cooling question comes up more and more often in our consultations – and the answer regularly surprises in both directions. The one surprise: that the geothermal probe can also cool almost free of charge on the side; for some builders, this was ultimately the tipping point in favour of the borehole. The other: that surface cooling does not replace an air conditioning unit. We have a sentence for this that has proven itself: «You will notice it in your feet and in your sleep – not on the thermometer.» Anyone who nods after this will be satisfied; anyone who actually wants 21 degrees in midsummer, we honestly offer something else or advise against it. And a planning detail from the projects: the desire for cooling almost always occurs in July and the heating replacement in October – whoever forgets the summer wish until the autumn quote, builds the option away unnoticed. Write it down.
Frequently asked questions
Can every heat pump cool?
No – cooling is a question of equipment: geothermal probe systems need the passive cooling function (heat exchanger, control), air-to-water units must be designed to be reversible. Both are decided during planning; ask specifically about this if you are interested in the option.
How cool does it realistically get with surface cooling?
A few degrees below what the room would otherwise have – noticeably more pleasant, even and without draughts, but not an air conditioning climate. The dew point limit prevents colder surfaces, and that is a good thing: it protects against condensation in the floor structure.
What does cooling cost in operation?
Passively via the geothermal probe: almost nothing – only circulation pumps and controls are running. Actively with a reversible air-to-water heat pump: the electricity consumption of the compressor, which on hot days is ideally covered by your own solar roof. Specific amounts depend on the system and usage.
Does cooling also work with radiators?
Practically no via the radiators – their small surface area is not suitable for cold water, and condensation would be inevitable. Surface systems such as underfloor heating are capable of cooling. However, those who only have radiators can get further with fan coils: they are connected to the same cold water circuit, actively blow the air over the heat exchanger and drain the condensate in a controlled manner.
Can I retrofit free cooling?
With an existing geothermal probe system, often yes – it requires a heat exchanger, changeover valves, dew point monitoring and a control system that recognises the cooling mode. Some manufacturers offer retrofit modules. The effort is significantly higher than what the same function would have cost when the system was built, but it is feasible in many boiler rooms.
Is free cooling also available with an air-to-water heat pump?
Not in this form. Free cooling uses a heat source that is cooler than the house in summer – this applies to the ground, but not to the outside air in midsummer. Air-to-water units cool actively via a reversible cooling circuit, and this feature must be present at the time of purchase: it cannot be added retrospectively.
Can a heat pump replace an air conditioning unit?
As a basic temperature control, often yes, as a cooling machine for a single hot room, no. Surface cooling works slowly and remains above a certain temperature for dew point reasons; an air conditioning unit acts immediately and dehumidifies in the process. In a well-shaded house, you usually do not miss the air conditioning unit – under an uninsulated roof, you do.
Does cooling cause moisture in the floor?
Not with professional execution: the system keeps the cold water temperature above the dew point and monitors the room humidity. That is exactly why the cooling function must be planned and adjusted – a system that is simply «turned colder» would indeed be a moisture risk.
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Sources: Fachvereinigung Wärmepumpen Schweiz FWS (system basics cooling); empirical values from the planning and project practice of ecoEn GmbH, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
