KCan I replace my heating system, which runs on fossil fuels oil and gas, with an electric heat pump – even if I don’t live in a well-insulated new building with underfloor heating or in an older building that has been completely renovated in terms of energy efficiency? Or to put it another way: does the heat pump also work in an old building? It is often said: Probably not, because without good thermal insulation and in connection with radiators, they are not very good.
Two weeks ago, on the other hand, we summarized in the FAS the results of a field test by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, which came to different and significantly more positive results for the heat pump: Although it makes sense, regardless of what type of heating you have, to comprehensively modernize an old building in terms of energy, i.e. to insulate the facade and roof and install well-insulated windows. But even in older buildings that do not meet these requirements, reasonable efficiency values can often be achieved with heat pumps, and they are also more climate-friendly – the conclusion of the Fraunhofer experts. In their study, the researchers continuously measured the efficiency of heat pumps in 41 old buildings, some of which had only been slightly renovated, for a year.
The FAS report was well received by readers. The results of the study were often questioned, while other readers reported good experiences with the installation of a heat pump in their by no means perfectly insulated old buildings. One question has also been raised again and again: Doesn’t the electricity bill get quite high if you use an electric heat pump to ensure pleasant temperatures in existing buildings? After all, for many years there have been complaints that electricity prices in Germany are among the highest in the world. So why heat with this expensive energy source of all things?
The heat pump uses free ambient heat
On the other hand, in contrast to oil or gas burners, heat pumps also use the free available thermal energy from the environment for heating, which increases their efficiency. The most popular are the so-called air-water heat pumps. They draw in outside air, which transfers its thermal energy to a refrigerant circulating in the device, which becomes gaseous even at very low temperatures. This vapor is compressed in an electrically powered compressor, causing the temperature of the vapor to rise – much like an air pump warms up when inflating a bicycle tire. The warm steam then transfers its thermal energy to the building’s heating system via a heat exchanger.
So which effect does the heat pump have more on your own wallet: the negative one due to the comparatively expensive electricity in Germany or the positive one due to the shared use of free ambient heat? The comparison portal Verivox compared the operating costs of gas heating and heat pumps for the FAS.