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Wärmepumpen ~ Heat pump

In recent years, heat pumps have been taking heating technology by storm and are seen as an environmentally friendly alternative to old-fashioned energy supply methods, most of which are based on the combustion of fossil fuels. What makes heat pumps so special? First things first: heat pumps draw heat from the environment, which is only delivered to a building's heating system through compression within the heat pump. This protects the air atmosphere, because less climate-damaging carbon dioxide is released for the purpose of generating heating energy than would be the case if oil, lignite or other fossil fuels were burned. On the other hand, heat pumps consume a fair amount of electricity, which ideally should be produced in a more climate-friendly way. If you have a sufficiently large roof or building area available for the installation of photovoltaic panels, then you have already half won at this point. Because by the supply of the current from the Photovoltaikmodullen is ensured for the climaticfriendly drive.  Apart from that, the efficiency of your building in combination with the chosen type of heat pump also plays a decisive role. If you have a well-insulated house, you will logically need less heating energy in the cold season than in houses with a poorly insulated building envelope.


Heat pump works in principle like an inverted refrigerator. While its cooling liquid dissipates the heat, a heat pump brings the heating energy into the house. The heat required for this comes from the ground, the groundwater or the outside air. If the heat requirement exceeds the output of the pump, further electricity is needed for an additional heating element. This electricity can, for example, come directly and cheaply from your own photovoltaic system on the roof or from a connected battery storage system. Heat pumps are therefore particularly worthwhile in this combination. However, they can of course also be operated using more expensive electricity from the wall socket.

A distinction is made between air-water, water-water and brine-water heat pumps.
The latter is also called a geothermal heat pump.The heat is obtained through pipes in which water with antifreeze circulates, or through fans that suc
k in the air.In the heat pump, they encounter a refrigerant that evaporates at low temperature.In a compressor, the vapor is compressed and thus heated.This heat is transferred to the heating circuit in the third step.A heat distribution and storage system collects the energy or distributes it directly in the house via underfloor heating or conventional radiators. Since the heat pumps draw most of the electricity they need from the photovoltaic modules, there is a time discrepancy between energy consumption in the evening hours and energy production during the sunny part of the day. To bridge this difference, buffer tanks are usually installed, which allow thermal energy generated during the day to be made available to building users in the evening.

Government funding

For the installation of a heat pump in an existing building, there is a basic subsidy of 25% of the purchase costs from the state. The share rises to 35% if it replaces an oil or night storage heating system or a gas heating system that is still functional and has been in operation for more than 20 years. A further 5% is granted if the heat source draws its energy from the ground, water or wastewater. A maximum of 40% funding is therefore possible for an existing building - with a cap of 60,000 euros per residential unit (as of the end of 2022).

There may also be regional funding pots. The German Heat Pump Association offers a subsidy calculator online, and Co2online also has a subsidy check.

Existing buildings

In existing buildings, heat pumps can only be considered if the buildings are well insulated and if the selected models fit the building's energy requirements.The decisive factor is the flow temperature of the heating system. This is the temperature of the water in the heating system.The lower it is, the more efficiently the heat pump works and the less electricity is consumed. Or, to put it another way, a heat pump in an unrenovated house with a high heat demand often leads to high energy costs.

"The bottom line is that cost-effective heating energy from renewable energy sources reduces CO2 emissions and provides a smaller environmental footprint. To ensure long-lasting and cost-effective heat pump operation, the system components selected should be well matched to the building characteristics.

Gebäude mit Solarheizung, Wärmepumpe, PV-Panelle
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