Heat Pumps in Existing Single-Family Homes

Wärmepumpen in Bestands-Einfamilienhäusern
© Fraunhofer ISE

Around 40 percent of all CO2 emissions in Germany are attributed to the provision of hot water and space heating for buildings. This is mainly due to the fact that inefficient gas and oil heating systems, which are harmful to the climate, are still being used in many existing buildings. In order to achieve the ambitious climate protection goals, it is necessary to equip existing buildings with heat pump systems. Good efficiency values are possible in older buildings! For building modernization, it makes sense to take a holistic approach in the planning, to reduce the building’s total energy demand, to interlink the different retrofit measures, and to optimally design the heat pump based on the specific building requirements. However, our analyses have shown that heat pumps can operate ecologically and economically even in buildings that have undergone little renovation.


  • more efficient operation possible
  • full building refurbishment unnecessary
  • long-term value enhancement for buildings
  • state funding
  • reduction of CO2 emissions compared to gas heating
  • use of own electricity from PV system

R&D on Heat Pumps in Existing Single-Family Homes:

  • optimization heat pump parameterization for building modernization
  • simplify heat pump installation
  • usage of natural refrigerants (focus on propane)
  • development safety concepts for flammable refrigerants
  • optimization of planning and efficiency during operation using artificial intelligence
  • analysis of load shifting potential of heat pumps in the field
  • optimization of extraction systems for environmental heat (outside air, geothermal energy, ground water, waste water, solar thermal energy) 

On This Topic from our Research Blog "Innovation4E":


Does a house have to be renovated first in order to install a heat pump?

Episode 3 of a series on heat pumps in existing buildings Clearly, the less energy needed to create a comfortable indoor climate, the better. That’s why renovation measures to reduce heating energy demand always make sense. This applies to all heating systems, not just heat pumps. For various reasons, (full) refurbishment of buildings is sometimes [...]
Read more


Are heat pumps able to deliver sufficiently high temperatures in the heating circuit?

Episode 2 of heat pumps in existing buildings: Why the maximum required temperature is not the decisive factor  When discussing the possible use of heat pumps in existing buildings, the main counter-argument is the very high temperature of the heating circuit on which they are based. The argument is that this temperature would lead to [...]
Read more


Heat pumps in existing buildings, a blog post series in 12 parts

Heat pumps are only suitable for new buildings or for buildings that have undergone an extensive energetical refurbishment! This is a common view that can be considered disproved in many respects today. Fortunately, one could say, because especially the existing buildings are crucial to achieve climate neutrality in the future. Around 75 percent of residential [...]
Read more

Marek Miara

Heat Pumps in Existing Buildings”, a Blog Post Series in 12 Parts

In the blog post series "Heat Pumps in Existing Buildings", our author Marek Miara answers the most pressing questions about heat pumps in existing buildings.

Our R&D Services on this Topic:

System Analysis and Optimization

Quality Assurance

Research Project

"WPsmart im Bestand"

Heat Pump Field Trial – Focus Existing Buildings and Smart Control