Appliances that deliver a flow of around 65 to 75 °C even on cold days are considered high-temperature heat pumps – enough for old radiators without any conversion. However, most Swiss old buildings do not need this class at all, because today's standard appliances with propane already reach quite high temperatures and the existing heating almost always runs hotter than the house requires. And high flow temperatures are not free of charge: every degree costs efficiency and therefore electricity. The correct sequence is therefore always: first measure how hot it really needs to be – then choose the appliance. (As of: September 2026)
Key points in brief
- «High temperature» is not a protected term, but a classification: it refers to appliances with a flow of around 65–75 °C, whereas standard appliances today typically go up to about 55–65 °C.
- Demand decides, not the year of construction: the reduction test on the existing heating usually shows that significantly less flow is sufficient.
- Every degree of flow temperature has an impact on efficiency – as a rule of thumb, it is around 2 to 3 percent of electricity per degree, and in Switzerland the kilowatt hour costs an average of 27.7 Rp./kWh.
- The cheaper alternative is almost always to lower the necessary flow temperature: one or two larger radiators and a hydraulic balancing instead of one appliance class higher.
- There are genuine cases for the high-temperature machine – protected building fabric, unchangeable heating surfaces, phased refurbishments. Then it is the right choice, but with an open calculation.
What defines a high-temperature heat pump
The term sounds like a separate technology, but primarily means a performance limit: how warm the appliance gets the heating water, not at the datasheet's optimum point, but when it is really cold outside. This is exactly where the classes separate.
Today's air-to-water heat pumps for the single-family home typically reach flow temperatures in the range of about 55 to 65 °C. Appliances that go beyond this and maintain around 70 °C even at low outside temperatures are classified as high-temperature appliances – this is the range in which old, tightly dimensioned radiators get warm without any adjustment. Above this, the industrial world begins: machines for process heat and district heating networks reach well over 100 °C, but have nothing more to do with the single-family home.
The reason why this class is even a topic lies less in new compressors than in the refrigerant. Propane (R290) has established itself in new air-to-water appliances and inherently brings high flow temperatures with it – what used to be reserved for special appliances, many standard machines can do on the side today. What needs to be considered for the installation site is covered in the article on the propane heat pump. For the purchasing decision, this means: the question «high temperature yes or no» is different in 2026 than five years ago.
Does your house really need high temperatures?
This question is almost always answered too early – namely with a glance at the old heating. If the oil boiler has a heating curve of 70 °C, the house is quickly considered a high-temperature case. This is the most common error in reasoning in the entire refurbishment discussion.
Because the setting of the old heating tells what someone set years ago, not what the house needs. Many buildings have received new windows since then, an insulated basement ceiling, a refurbished roof – the heating curve simply continued to run as before. In addition, radiators in old buildings were often generously dimensioned. Both together mean that the actual demand is regularly 10 to 20 degrees below the set temperature.
The test for this costs nothing: step-by-step lowering of the flow temperature of the existing heating, observe over cold days, note rooms that can no longer keep up. If the house remains comfortable, the high-temperature question is resolved before it was asked. The whole procedure with its limits is in the article heat pump in an old building – it answers the question of suitability, this one answers the question of appliances.
And a second point belongs to this: it is rarely the whole house that limits, mostly it is one or two rooms – the bathroom, the corner room facing north. This is crucial for the choice of appliance, because a single room never justifies running the entire system at a high temperature level.
What high flow temperatures cost
This is the core, and it is often skipped in sales talks: a heat pump raises heat from the source to the level of the heating water. The larger this lift, the more electricity it needs for the same heat. This applies to every machine, even to the best high-temperature machine – it manages the high temperature, it just does not manage it for free.
As a rule of thumb in the industry, around 2 to 3 percent more electricity consumption applies per degree of higher flow temperature. This is a practical classification and not a basis for calculation, but it makes the magnitude tangible. An example with round numbers shows what becomes of this: A single-family home with a heat demand of 12,000 kWh per year needs around 3,750 kWh of electricity with a seasonal performance factor of 3.2. If the seasonal performance factor falls to 2.6 due to a permanently high flow temperature, it is a good 4,600 kWh – around 850 kWh more, every year.
With an average Swiss electricity price of 27.7 Rappen, that is about 240 francs per year. Over the lifespan of a heating system, this adds up to a four-figure sum – namely for a temperature that many houses do not even need. The figures are guideline values for orientation; what your system actually consumes depends on the building, dimensioning and setting.
| Appliance class | Flow on cold days | Typical application | Consequence for efficiency |
|---|---|---|---|
| Standard (today's appliances) | around 55–65 °C | New building, refurbished old building, generous radiators | Efficiency in the expected range |
| High temperature | around 65–75 °C | Old building with limited heating surfaces that cannot be altered | noticeably lower seasonal performance factor, higher electricity costs |
| Industry / process heat | over 90 °C | Business, district heating, processes | separate design, not an issue in the single-family home |
Qualitative classification, As of: September 2026 – the datasheet of the specific appliance and the dimensioning on the building are decisive.
The alternative: lowering the necessary temperature
Anyone who has seen the calculation from above arrives almost automatically at the other direction. Instead of buying the appliance one class higher, you lower what the house demands – and that is in the vast majority of cases the smaller intervention.
The biggest lever is the one or two limiting rooms. A larger or a low-temperature radiator there shifts the temperature level of the entire system downwards, because the heating curve is always oriented towards the worst room. In addition, there is the hydraulic balancing, which allocates its water quantity to each radiator: without it, the system runs hotter than it would have to, just so that the last room can also keep up. The role played by heat distribution overall is in the article underfloor heating or radiators.
The calculation is usually clear: two radiators and a balancing cost once – the higher flow temperature costs every year, as long as the system is running. That is why the sequence in our consultation is always the same: first check whether the demand can be lowered, and only then talk about the appliance class.
When the high-temperature machine is nevertheless right
There are these cases, and they deserve a clear answer instead of a detour. Three constellations regularly occur in practice.
The first case is the protected building fabric: where radiators, stucco or pipe routing may not be altered, the cheaper alternative falls away. What applies to protected objects is dealt with in the article on heritage protection – by analogy, it also applies to the heating side. The second case is the phasing: anyone who knows that insulation or window replacement will only come in a few years, but now has a dead boiler, needs a machine that can serve both states – hot today, cooler later. The third case is buildings with really limited heating surfaces, where the reduction test is clearly negative and a conversion would be disproportionate, for instance in apartment buildings with many flats.
In all three cases, the high-temperature heat pump is the right solution – with an open calculation: higher electricity costs in operation, but no intervention in the heat distribution. Those who know this beforehand are more satisfied than someone to whom the electricity bill is explained later.
What additionally matters in Switzerland
Two things differentiate the Swiss decision from what you read in German guides.
The incentives depend on the procedure, not the appliance type. The replacement of a fossil or electric heating system receives cantonal incentives, and the rules for this are formal: the application must be submitted before construction begins, and for systems up to around 15 kW, the cantons generally require the Heat Pump System Module (WPSM) installation certificate. Which contributions apply where can be found in the articles on heat pump incentives in Switzerland and on incentives in the Canton of Zurich. For the appliance class, this means: high temperature does not exclude the incentives – but the sequence application-before-start-of-construction applies unchanged.
And the electricity price makes the difference more expensive. The difference in operating costs from the calculation example above meets a price level that varies greatly depending on the grid area. Those who need a lot of electricity for high flow temperatures feel this correspondingly more clearly – and conversely, exactly for these houses, your own roof electricity becomes interesting. The article combining heat pump and photovoltaics shows how both are connected; however, for the winter demand of a high-temperature system, your own solar system is the weakest answer, because that is when the least sun comes.
Another practical tip that often only appears late: appliances that deliver high temperatures work harder – this is also an issue for noise and the installation site, and the authorisation questions remain the same as with any other heat pump.
The high-temperature question almost always comes to us with the same background: someone has read online that their own old building needs a special machine, and wants a quote for exactly this. Our first answer is therefore not a quote, but an assignment for the client – gradually lower the heating curve over a few cold weeks and note down where it gets stuck. In the vast majority of cases, the feedback comes that it remained comfortable everywhere, often with surprise at the range. What remains are one or two rooms, and we solve these with radiators, not with an appliance class. The cases in which we ultimately do plan a high-temperature machine usually have a reason that has nothing to do with technology: protected building fabric or a refurbishment that is only due in five years. But then we also say what this means in operation – better beforehand in conversation than afterwards on the electricity bill.
Frequently asked questions
What is a high-temperature heat pump?
A classification for appliances that deliver flow temperatures of around 65 to 75 °C even at low outside temperatures. This allows old radiators to get warm without the heat distribution having to be changed. The term is not protected; the datasheet of the specific appliance is decisive.
Does an old building always need a high-temperature heat pump?
No, in most cases not. The existing heating often runs hotter than necessary because the setting was never adapted to new windows or insulation. The reduction test on the old heating shows which temperature the house really demands before any purchasing decision.
How much electricity does a high flow temperature cost?
As a rule of thumb, it is around 2 to 3 percent more electricity per degree. In a single-family home with a heat demand of 12,000 kWh, the difference between a seasonal performance factor of 3.2 and 2.6 can amount to around 850 kWh of electricity per year – at average Swiss electricity prices, towards 240 francs annually. The values are guideline values for orientation, not your system.
What is cheaper: high-temperature appliance or new radiators?
As a rule, the radiators. Mostly, only one or two rooms limit; larger or low-temperature radiators there lower the temperature level of the entire system. The conversion costs once, the high flow temperature costs every year of operation.
Do normal heat pumps today reach higher temperatures than in the past?
Yes. With propane as a refrigerant, many standard appliances reach temperatures that used to be reserved for special machines. Therefore, the question of the high-temperature class is less often answered in the affirmative today than a few years ago.
Is a high-temperature heat pump incentivised in Switzerland?
The replacement of fossil and electric heating systems with heat pumps is incentivised, regardless of how high the appliance's flow temperature reaches. The cantonal conditions are decisive: application before start of construction and, for systems up to around 15 kW, generally the WPSM installation certificate.
Which manufacturer builds high-temperature heat pumps?
Several established manufacturers carry appliances of this class; individual providers have specialised in them. We work independent of manufacturers – which appliance fits is decided by the required flow temperature, the space and the local service partner, not by the brand. An overview is provided by the article on heat pump manufacturers.
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High temperature or not? We measure it before we quote.
We look at the heating curve, heating surfaces and building and tell you honestly which flow temperature your house really needs – even if the answer turns out to be cheaper than expected. Advice from the region, without sales pressure.
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Sources: EnergieSchweiz/SFOE (Recommendation of lowest possible flow temperatures, SPF guideline values – via /jaz-waermepumpe/); ElCom electricity prices 2026 (Average 27.7 Rp./kWh – via /strompreise-schweiz-entwicklung/); Fachvereinigung Wärmepumpen Schweiz FWS (Heat Pump System Module WPSM); cantonal incentive conditions (via /foerderung-waermepumpe-schweiz/ and /waermepumpe-foerderung-zuerich/); manufacturer datasheets on flow temperature ranges; empirical values from the planning and installation practice of ecoEn GmbH, Zurich region. (As of: September 2026)
Last updated: 9 July 2026 · Author: ecoEn editorial team
