A heat pump should not simply be ordered from a catalogue. Most problems do not arise from the technology itself, but from planning errors: incorrect output, flow temperature that is too high, lack of sound insulation or an incomplete quote. The good news: these errors are known – and can be well avoided with the right preparation. This overview summarises the most common ones and refers to the in-depth guides.
The most important points in brief
- Common errors relate to building inspection, flow temperature, and sizing.
- The old boiler output is not a good benchmark for the new system.
- Sound insulation must be clarified early for air-to-water systems.
- Subsidy applications are often submitted too late.
- Domestic hot water and storage are regularly underestimated.
- Several complete quotes significantly reduce the risk of poor decisions.
- As of 12.07.2026
- Sources at the end of the article
Mistake 1: Not checking the building
Without reliable building data, no serious planning is possible. Insulation, windows, radiators and actual heat demand must be known. Especially in existing buildings, the condition of the property determines whether and how well a heat pump works. How to assess this is shown in Heat pump in an older building.
Mistake 2: Underestimating the flow temperature
The flow temperature is the most important efficiency factor. High flow temperatures reduce the seasonal performance factor (SPF) and may necessitate additional measures – such as replacing individual radiators. How heating surfaces and temperature are related is explained in Heat pump with radiators.
Mistake 3: Incorrect sizing
An oversized system may cycle more frequently and operate less efficiently; an undersized system can cause comfort issues or require supplementary heating more often. The benchmark is the calculated heating load, not the old boiler output. Details: Sizing a heat pump.
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Mistake 4: Forgetting sound insulation
With air-to-water heat pumps, an unfavourable location can lead to conflicts with neighbours and problems obtaining a permit. Location, equipment selection and the proof of noise compliance should be considered early in the planning stage. More on this: Noise protection for heat pumps.
Mistake 5: Underestimating domestic hot water
Domestic hot water is no detail. Tank size, temperature and Legionella protection influence comfort and efficiency. Those who plan the storage concept only at the end risk reduced comfort or unnecessary electricity consumption. Details: Domestic hot water with a heat pump.
Mistake 6: Checking the subsidy too late
Subsidy applications must generally be submitted before construction begins. Anyone who starts installation before the application has been submitted or approved may lose their entitlement to the subsidy; the exact rules depend on the cantonal programme. The programmes vary by canton and are not guaranteed – an early assessment is worthwhile. Overview: Heat pump subsidies in Switzerland 2026.
Do not miss subsidy deadlines The specialist partners know the procedures and deadlines at your location. Through waermepumpen-guide.ch you can reach up to three suitable specialist installers from your region – free of charge and without obligation. Compare quotes for free
Mistake 7: Only comparing purchase costs
The lowest price is not automatically the best offer. Dismantling, storage, electrical work, service, subsidy assumptions and sound insulation should be included in the comparison – otherwise you are comparing apples with pears. What a heat pump really costs is shown in What does a heat pump cost in Switzerland?.
Mistake 8: Only obtaining one quote
Those who only obtain one offer have no basis for comparison – neither in terms of price nor planning. Two to three complete quotes make differences in system choice, sizing and equipment visible. What you should pay attention to is shown in the Checklist for comparing quotes.
Overview: the most common mistakes
| Error | Result | In-depth information |
|---|---|---|
| Not assessing the building | unrealistic planning | Heat pump in an older building |
| Underestimating the flow temperature | poor efficiency | Heat pump with radiators |
| Incorrect sizing | Cycling or comfort issues | Sizing a heat pump |
| Forgetting sound insulation | Conflicts and remediation | Noise protection for heat pumps |
| Underestimating domestic hot water | Loss of comfort and efficiency | Domestic hot water with a heat pump |
| Subsidy too late | subsidy at risk | subsidy Switzerland 2026 |
| Comparing only the price | wrong decision | Costs in Switzerland |
| only one quote | no basis for comparison | compare quotes |
Checklist for good planning
- Record building data and heat demand
- Check flow temperature and heating surfaces
- Calculate heating load (do not take over boiler output)
- Determine the domestic hot water and storage concept
- Clarify location and sound insulation early on
- Submit subsidy application before construction begins
- obtain complete quotes from several specialist installers
How different good planning can look is shown by three typical cases: the location selection for the air-to-water heat pump, the early system integration in a new build with heat pump, and the complete dismantling in the project Replacing oil heating with a heat pump.
When is it worth comparing multiple quotes?
Almost all of the errors mentioned can be mitigated by a good comparison of quotes: It makes planning, sizing and equipment transparent and shows which specialist installer works cleanly. Two to three complete quotes are usually sensible for this purpose.
Conclusion
Good planning saves costs, energy and hassle. The most common errors concern building inspection, flow temperature, sizing, sound insulation, domestic hot water and subsidies – and they can all be avoided. A complete quote and the comparison of multiple specialist installers are the best protection against wrong decisions. An overview on the topic is provided by Heat pump in Switzerland.
Compare heat pump quotes Through waermepumpen-guide.ch, you can submit your request free of charge and without obligation. Your request will be forwarded to up to three suitable specialist installers from your region, who will prepare individual quotes. Compare quotes for free
Frequently asked questions and answers
What is a common mistake in heat pump planning?
An unsuitable sizing or a flow temperature that is too high are among the common errors. Both can have a significant impact on efficiency and costs.
Why is sound insulation important?
Because an unfavourable location for air-to-water heat pumps can affect neighbours and the permit. It should be planned early on.
Should you obtain multiple quotes?
Yes. Two to three complete, comparable quotes are sensible to assess planning and price.
When must the subsidy application be submitted?
Usually before construction begins. Those who start too late lose their subsidy entitlement. The programmes vary by canton.
Can design errors be corrected afterwards?
Partially, but often with high effort and costs. Careful planning from the start is significantly cheaper.
Sources and further information
- SwissEnergy / Swiss Federal Office of Energy (SFOE): Planning and efficiency of heat pumps
- Swiss Heat Pump Association (FWS): Planning, quality and sound insulation
- The Buildings Programme / Energiefranken: subsidy programmes by location (as of 2026)
- Standard SIA 384/2: Heating load of buildings
- Cercle Bruit: Legal assessment of noise from air/water heat pumps
