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Heat pumps: Efficient

Even in existing buildings


The fact that electrically operated heat pumps are also suitable for efficient deployment in existing buildings has now been confirmed by the Fraunhofer Institute for Solar Energy Systems (ISE) – based on field tests covering the last twelve years.

Heat generator established

in the new buildings segment

Electrically operated heat pumps have made a good impression in new buildings for many years. Last year, more than 37% of all newly-constructed residential buildings were equipped  with systems using environmental heat or geothermal energy. Air-to-water heat pumps were by far the most popular option, with the 37,745 installed systems clearly exceeding the 8,973 geothermal energy systems that were fitted.

Long-term test results also favour use of

air-to-water heat pumps in existing buildings

In a recent test, the Fraunhofer Institute additionally determined that air-to-water heat pumps are also suitable for successful deployment in modernisation. This is because the efficiency of this technology has increased considerably over the last ten years – by around 20 per cent.

The recent heat pump test featured assessments of buildings constructed between 1950 and 1995. There are many layers behind the reasons for this significant increase in efficiency: not only have manufacturers enhanced heat pump technology, but the installations and heat transfer systems have also been improved. In the 15 systems that were measured, the average annual performance factors of the air-to-water heat pumps were between 2.5 and 3.4, with one thoroughly renovated building achieving an annual performance factor of 4.1.

Turning to the near future

Cleaner heat generation

Dr Marek Miara, Heat Pumps Coordinator at the Fraunhofer ISE, sees even more potential in heat pump technology: “In the future, heat pumps will develop into the most important heating technology in Germany. In 2050, they are expected to provide between 65 and 90 per cent of low-temperature heat in buildings.” (Source:

The Agora think tank has also forecast positive further development for heat pumps in studies such as ‘Heat Transition 2030. Key technologies for reaching the intermediate and long-term climate targets in the building sector’. In terms of climate protection, the intention here is for oil heating boilers to be largely replaced by heat pumps by the year 2030. In order for this goal to be achieved, Agora expressly recommends the use of heat pumps in existing buildings – together with peak load boilers that are still powered by fossil fuels if necessary.

Monovalent or monoenergetic

heating in existing buildings

The latest heat pump technologies from Mitsubishi Electric enable reliable heating in existing buildings using a heat pump – without the need for a peak load boiler. A monovalent heat pump layout is often possible in this context, depending on the situation of the building. This means that the heat pump provides sufficient heating output without an additional boiler or the use of an electric heating rod.

Even in economic terms, however, it often makes sense to use a monoenergetic layout for the heat pump system in existing buildings. It is frequently possible to use a heat pump featuring a lower heating output in such cases, with the heating rod being activated on a small number of particularly cold days. As this only occurs very rarely, this is often an excellent solution when it comes to considering the overall costs.