ENERGY KNOW-HOW
Not all heat pumps are the same. Depending on where they draw their heat from, efficiency, costs and effort differ considerably. Here you can compare the four types and see what they mean for the value and sale of your house.
| Air-to-water | Brine-to-water (ground source) | Water-to-water (groundwater) | Air-to-air | |
|---|---|---|---|---|
| Heat source | Outside air | Ground (borehole probe or collector) | Groundwater (two wells) | Outside air, heats the indoor air directly |
| Efficiency (typical SPF) | approx. 3.1 | approx. 4.1 | up to approx. 5 | depends on the unit, no hot water |
| Costs for a detached house | approx. €29,500 | approx. €30,500 + €8,000–16,000 for drilling/collector | approx. €28,500 + €8,000–16,000 for wells | considerably cheaper, more suited to individual rooms |
| Permit | usually none; observe distance and noise protection rules | water law permit for drilling | water law permit; water must be suitable | usually none |
| Space | 0.5–1.2 m² outdoor unit | drilling site or larger garden area | two wells 10–15 m apart | indoor and outdoor units |
| Well suited to | most houses, including existing buildings | houses with a plot, high heat demand | plots with suitable groundwater | well-insulated apartments, as a supplement |
| Points to note | less efficient in frost, noise from the outdoor unit | higher initial costs, drilling must be possible | well construction more complex, check water quality | generally not eligible for the heating subsidy |
SPF = seasonal performance factor (JAZ): how many kilowatt hours of heat are produced from one kilowatt hour of electricity. Higher is better. Costs and SPF are average values according to co2online (as of September 2026); individual cases may differ significantly.
| Component | Grant | Who is eligible |
|---|---|---|
| Basic subsidy | 30 % | all private owners and owners’ associations (WEG) |
| Climate speed bonus | 16 % | Owner-occupiers replacing an oil, coal, gas floor-unit or night storage heating system, or a gas or biomass heating system at least 20 years old. 16% for applications up to 31/01/2027, then reduced by 4 percentage points every six months |
| Income bonus | 10–40 % | Owner-occupiers: 40% up to €30,000, 30% up to €40,000, 10% up to €50,000 taxable household income; with a child under 18, each threshold is €10,000 higher |
| Maximum rate | 70% (80% for low incomes) | based on max. €28,000 eligible costs for the first residential unit |
As of: applications from 21 July 2026, according to cleanthinking.de. From 01/02/2027, the climate bonus and maximum amount will be reduced gradually; a lower basic subsidy has been announced for heat pumps manufactured outside the EU. Please check the current conditions directly with KfW before placing an order.
Not necessarily. What matters is the flow temperature your house needs on cold days. Larger radiators in individual rooms are often enough. This can be checked on site.
No. With the new Building Modernisation Act, the 65 per cent rule for new heating systems has been abolished. However, from 2029 new gas and oil heating systems must use a share of renewable fuels, and the CO2 price is making fossil-fuel heating more expensive.
Often yes, because part of the electricity comes from your own roof. How much depends on the system, storage and consumption. In the PV & energy check, I look at both together.
A modern, efficient heating system makes a house more attractive to buyers because they can better assess running costs and future obligations. How strongly this is reflected in the price depends on the individual case.
This page does not replace energy advice or a heating load calculation. For planning the system, a specialist contractor and an energy efficiency expert are the right people to contact. I am happy to assess what it means for value and sale.