R290 is pure propane and has become the standard for new air-to-water heat pumps. Two reasons: The greenhouse effect is orders of magnitude lower than that of synthetic refrigerants, and propane easily reaches high flow temperatures – which suits older buildings with radiators. The price for this is flammability: it determines where the device may be placed. (As of: August 2026)
Key points in brief
- R290 is propane – a natural refrigerant with a greenhouse potential close to zero, compared to the synthetic agents of earlier device generations.
- The practical advantage for homeowners is called flow temperature: propane devices reach the temperatures that an older building with radiators needs on cold days.
- The disadvantage is not poorer technology, but a location issue: a flammable refrigerant means requirements regarding distances, openings and light wells.
- For outdoor installation – i.e. the most common design in Switzerland – this is unproblematic in most cases.
- Whether there is propane in the device is stated in the data sheet. Ask about this during the consultation before you determine the installation location.
What R290 actually is
The refrigerant is the working fluid inside the heat pump: it evaporates at a low temperature, is compressed and releases the heat again in the condenser. Which substance passes through this cycle is not noticed in everyday life – it nevertheless changes a lot about the behaviour of the device. The basics of this can be found in the article Refrigerants in the heat pump.
R290 is the technical designation for refrigeration-grade propane. It belongs to the natural refrigerants, is not patented, has been known in refrigeration technology for decades – and was a niche product for a long time because synthetic agents are easier to handle. The fact that it is now found in almost every new air-to-water device has two causes: regulatory pressure on agents with a high greenhouse potential and a technical advantage that manufacturers underestimated for a long time.
The advantage that counts in older buildings: flow temperature
For houses with underfloor heating, the question of refrigerant is secondary – moderate flow temperatures are sufficient there, and practically every device delivers them efficiently. Propane becomes interesting for the other half of the Swiss building stock: older buildings with radiators, which need significantly higher flow temperatures on the coldest days.
This is exactly where R290 plays to its strengths. Propane devices achieve the higher flow temperatures without the drop in efficiency that older refrigerants showed in this range – and without an electric heating element necessarily having to step in. This noticeably pushes upwards the limit at which we have to advise replacing radiators or taking insulation measures. What this means in concrete terms can be found in the articles Heat pump in an older building and Heat pump with radiators.
Secondly, the environmental aspect. If refrigerant escapes – in the event of a leak or improper disposal – it acts as a greenhouse gas. With synthetic agents of the latest generations, this effect is considerable, whereas with propane it is practically negligible. For the ecological balance of a heating system that runs for twenty years, this is not a peripheral issue.
| Propane (R290) | older synthetic refrigerants | |
|---|---|---|
| Greenhouse potential | very low | partly very high |
| High flow temperatures | well suited | limited depending on the agent |
| Flammability | flammable – requirements for the installation location | non-flammable |
| Regulatory perspective | future-proof | increasingly restricted |
| Availability 2026 | Standard for new air-to-water devices | phasing out |
Qualitative comparison, as of: August 2026. The information in the data sheet of the specific device is authoritative.
The disadvantage: propane burns – what does that mean for the installation location?
Accuracy is worthwhile here because the topic often seems bigger in conversations than it is.
Propane is flammable. Therefore, requirements apply to devices with R290 regarding how much refrigerant is allowed in the circuit and where the device must be located – especially with regard to distances to windows, doors, basement stairs and light wells. The idea behind this: propane is heavier than air and would spread downwards in the event of a leak instead of evaporating.
For the outdoor installation of a monobloc device, which is common in Switzerland, this is no obstacle in the vast majority of cases. The refrigeration circuit remains completely in the outdoor unit; only water pipes enter the house. The manufacturer's installation specifications as well as the relevant safety standards for refrigeration systems and the cantonal fire protection requirements are authoritative – the specialist company checks this when choosing the location, together with the sound assessment, which is necessary anyway.
It becomes more restrictive with indoor installation and with split devices where part of the refrigeration circuit is located inside the building. There, the requirements limit the permissible amount of refrigerant in relation to the room volume, and depending on the situation, requirements for ventilation or the installation room are added. This does not exclude propane indoors, but makes it a planning issue rather than a matter of course.
Important for context: these requirements are not a warning sign of a risky device, but the reason why you never notice them in everyday life. The amount of refrigerant in a domestic heat pump is in an order of magnitude that many know from their garden barbecue – and in contrast to this, the circuit is factory-closed, tested and not intended to be opened.
What does this mean for your purchasing decision?
In practical terms, little effort and clear advice: if you buy an air-to-water heat pump for a single-family home in 2026, it will most likely be a propane device anyway. The question is therefore less «Propane yes or no?» than «Does the planned location suit this device?».
Three points therefore belong in the quote:
1. Which refrigerant is installed in the offered device – the information is in the data sheet, not in the brochure. 2. How was the installation location chosen – with what distances to openings, light wells and property boundaries, and is the sound assessment part of it. 3. Who maintains the device – work on the refrigeration circuit is the responsibility of an appropriately qualified company; this applies all the more to flammable agents. What belongs in a maintenance contract can be found in the article Heat pump: Maintenance and lifespan.
What propane does not solve: a device becomes neither quieter nor cheaper due to the refrigerant, and an undersized system remains undersized. Efficiency in everyday life continues to be determined by sizing, hydraulics and settings – that is where the big levers lie, not in the refrigerant.
The propane question now comes up in almost every consultation with us, and mostly in the form: «Isn't that dangerous?» Our answer is unspectacular – with outdoor monobloc devices, such as those we predominantly build in the region, practically nothing changes for the operator. Where we really look twice is the location: we will replan a device that is to be placed directly next to a basement light well or in an enclosed inner courtyard – not because of an acute danger, but because the manufacturer's specifications simply require different distances there. And in one respect, propane has actually changed our advice: for older buildings with radiators, where a few years ago we still had to talk about replacing radiators, the device alone is now often sufficient.
Frequently asked questions
What does R290 mean for a heat pump?
R290 is the refrigerant designation for propane. It is a natural refrigerant with a very low greenhouse potential that efficiently achieves high flow temperatures. It is the standard for new air-to-water heat pumps in 2026.
What are the disadvantages of a propane heat pump?
Propane is flammable. This results in requirements for the installation location – distances to windows, doors and light wells – and, for indoor installation, requirements for room volume and ventilation. With the usual outdoor installation, this can mostly be solved without additional effort. A device does not become quieter or cheaper through propane.
Is a propane heat pump dangerous?
No, not if installed professionally. The refrigeration circuit is closed and tested at the factory, and the filling quantity is small. The safety requirements concern the planning, not the operation – which is why the choice of location belongs in the hands of the specialist company.
Is propane suitable for an older building with radiators?
This is the constellation in which R290 makes the biggest difference: propane devices reach the higher flow temperatures that radiators need on cold days without the electric heating element necessarily having to step in. A heat load calculation will clarify whether your house can be operated in this way.
Can I install a propane heat pump in the basement?
In principle, yes, but it is a planning issue: for indoor installation, the requirements limit the amount of refrigerant in relation to the room volume; sometimes requirements for ventilation are added. In Switzerland, outdoor installation predominates for air-to-water devices anyway.
Are propane devices more expensive?
Not systematically. The price arises from the performance class, equipment and manufacturer, not from the refrigerant. The guideline values for the entire heating replacement can be found in the article Heat pump costs Switzerland.
Free initial consultation
Does the device suit your location?
During the site visit, we look at where the heat pump can be placed – distances, sound, pipe runs – and tell you which device class makes sense for your house and your flow temperature.
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Swissolar-certified specialist company · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: Manufacturer data sheets of standard market air-to-water heat pumps 2026, safety standards for refrigeration systems (SN EN 378), cantonal fire protection requirements, ecoEn project experience.
Last updated: 9 July 2026 · Author: ecoEn editorial team
