Heat Pump PLUS

Heat pumps transfer heat from the ambient air, groundwater or the ground into buildings. A refrigerant circulating in a closed loop absorbs heat and evaporates in the process. An electrically powered compressor compresses the refrigerant, which is now in a gaseous state, causing its temperature to rise significantly. It is precisely this temperature increase caused by pressure that is the key factor. This is because, in another component – the condenser – the refrigerant, at high pressure and consequently high temperature, transfers thermal energy to the heating system. In the process, it returns to a liquid state and, once the pressure – and thus the temperature – has been reduced again by the expansion valve, it can once more absorb heat from the environment.

Due to their design, air-to-water heat pumps are more affordable than groundwater or geothermal heat pumps. They draw their energy from the ambient air and convert it into heat to heat rooms and provide hot water. They represent an environmentally friendly and cost-effective alternative to conventional heating systems. By 2025, just under 300,000 air-to-water heat pumps had been installed across Germany – significantly more than gas condensing boilers, which had long been the most popular heating system in Germany.

Heat pumps are capable of generating heat even on freezing winter days, although their efficiency does decrease as the outside temperature drops. That is why the vast majority of units are fitted with an electric heating element as standard. This is a type of immersion heater which switches on when the heat pump’s output drops, providing additional support.

The annual performance factor (APF) expresses the ratio of the useful heat generated to the electrical energy used to produce it. It therefore describes the system’s efficiency over a full year. A system with an APF of 4 thus generates, on average over the year, four kilowatt-hours of heat from just one kilowatt-hour of electricity.

In real-world operation, the JAZ in Germany ranges from 3 to 3.5 – and can be even higher for well-planned systems, i.e. those tailored to the specific building. Important to note: The JAZ is not a fixed value, but a practical indicator that depends on various factors. In addition to the prevailing outdoor temperatures, usage patterns and various technical aspects play a role, all of which must be taken into account during the planning stage.

Air-to-water heat pumps are considered extremely reliable. Experience from countries where heat pumps have been the norm for much longer shows that the units operate without any problems for 20 years or more. And this is true even under more challenging conditions – such as in Sweden or Switzerland. Furthermore, heat pumps score highly due to their noticeably lower maintenance requirements compared to oil and gas systems. Most manufacturers recommend annual checks. However, unlike with oil or gas burners, these are not mandatory. Nor is there any need for regular tank cleaning or visits from a chimney sweep.

Heat pumps are usually powered by green electricity. This means that, from day one, you save 100 per cent of the CO₂ emissions generated by heating and hot water production. The absolute amount saved therefore depends on the original system that was replaced by the heat pump. In a typical older detached house, several tonnes of CO₂ can usually be saved each year.

Yes, the cost of a heat pump is eligible for a grant. In Germany, grants of up to 70 per cent of the purchase price are available when switching from an oil or gas heating system. Our energy advisory service at the SWG Customer Centre on Marktplatz will be happy to provide you with comprehensive advice on grants.

Yes – in the vast majority of cases, making the switch is worthwhile. This is always provided that the heating requirement is calculated correctly and the system is sized accordingly. The extent of the savings, of course, depends crucially on how energy prices develop. One thing is certain: fossil fuels are becoming increasingly expensive due to the foreseeable rise_{in CO₂ pricing}. In contrast, there are special green electricity tariffs that are significantly cheaper than those for domestic electricity. Recent real-world examples show operating cost savings of between 50 and 80 per cent.

Incidentally: as early as 2024, the Fraunhofer Institute concluded in its Ariadne study that heat pumps pay for themselves over 20 years in older buildings. In energy-efficiently refurbished buildings, they pay for themselves much more quickly. And in new-builds, they are in any case the most economical option among individual heating systems.

Air-source heat pumps are usually installed outside buildings, in gardens or on terraces. This allows them to draw in air, extract heat from it and then use this heat to warm both the house and the water. The space required is usually just a few square metres, plus any necessary gap between the heat pump and the house wall. This gap is needed to allow for good air circulation.

In short: negligible. The heat pump’s outdoor unit does produce some noise. This is around 60 decibels, which is comparable to a normal conversation. The highest noise levels occur during the winter months – that is, when the windows are closed and nobody is spending time in the garden, on the patio or on the balcony any longer.