Energy transition

Heat pumps as a contribution to energy independence and climate protection: how their implementation can succeed

In order to achieve its climate goals and move towards more energy independence, the German government is planning a 100-billion-euro support package. In that context, the CO2 reduction targets for existing buildings are coming into focus. There is great potential in the provision of space heating and hot water supply alone: Energy-efficient heat pumps can support the shift from fossil fuels and contribute to more energy independence. For this to happen, however, the number of heat pumps must increase dramatically – from currently one million to approximately four to six million by 2030. Energy experts from the ISOE – Institute for Social-Ecological Research have investigated what hinders the wide-scale deployment of this technology and how barriers can be overcome.

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Himmel mit Sonne und Wolken (Foto: Jose Ignacio Soto -
Sky with sun and clouds (Photo: Jose Ignacio Soto -

Heat pumps play a central role in the ecological conversion of the building sector as planned by the German government. In the long term, they can replace conventional CO2-intensive oil and gas heating systems. They do this by using ambient heat from different sources such as soil, groundwater and air for heating and they can be operated with renewably generated electricity. “In order to meet the Paris climate targets, the potential for greenhouse gas reductions in buildings that can be achieved by switching  to heat pumps should be exploited as quickly as possible”, says ISOE energy expert Immanuel Stieß. “There is a great need to catch up, especially in apartment buildings. Here, heat pumps are still hardly in use.”

Particularly as part of so-called trigeneration systems, which combine heating, cooling and electricity generation, heat pumps can significantly lower the ecological footprint and at the same time reduce electricity and heating costs. In the European research network "TRI-HP – Trigeneration systems based on multiple renewable sources”, in which Immanuel Stieß and his team were involved, such systems were investigated. “A large part of the electricity needed to operate trigeneration heat pumps can be generated on site by photovoltaics”, says Stieß. “The use of solar energy from one’s own roof makes the operation of these heat pumps particularly energy-efficient, self-sufficient and more cost-effective than fossil-fuelled heating systems.”

Technology for next-generation heat pumps

Another advantage of these innovative heat pump systems is that they do not use synthetic refrigerants, which have a very high global warming potential. Instead, they use natural refrigerants such as propane or CO2, which makes their operation very environmentally and climate-friendly. “In this combination, trigeneration systems represent the technology for next-generation heat pumps, a key technology on the path to greater sustainability and more independence from fossil fuels”, says Stieß.

However, the ISOE researcher also knows that technology alone is not enough to protect the climate. Technical innovations must also be known to and accepted by users and decision-makers. In four European countries, including Germany, Stieß and his colleagues investigated in a multi-stage dialog process with various stakeholders the non-technical barriers and drivers of heat pumps. Together with investors, architects, property owners and installers they explored which economic, organisational and communicative requirements and needs have to be taken into account for this technology to be implemented successfully.

Energy-efficient solutions in the heating sector are ecologically and socially necessary

“The stakeholder dialogues have shown that the greatest challenge for the installation of heat pump systems lies in existing buildings”, says Immanuel Stieß. “The reason for this is that the switch to a heat pump, like any refurbishment to improve energy efficiency in existing buildings and flats, must be planned well. This involves initial investment costs that are later compensated for by lower operating costs.” For new buildings, however, the energy expert sees a good window of opportunity to establish the energy-efficient systems. According to current plans by the German Federal Ministry of Economics and Climate Protection, every newly installed heating system must be operated on the basis of at least 65 percent renewable energies from 2025.

Moving away from fossil fuels for heating as quickly as possible, however, is crucial not only in terms of climate targets, but also from a societal perspective. “Especially households in rented flats have to spend an even larger share of their income on energy costs due to the currently enormously rising prices for fossil fuels. This contributes significantly to the burden on low and middle income groups.”

Understanding the overall system: Training campaign for trade associations and manufacturers

In order for the heat transition to make progress, the ecological importance of heat pumps for reducing greenhouse gas emissions must first be made known to the public. But there is also a need for action at the planning level. The stakeholders surveyed in Germany, Switzerland, Spain and Norway mentioned the higher effort required for successful planning and installation of innovative heat pumps as well as the associated high investment and upfront costs as a major obstacle. “There is a lack of blueprints for simplified planning that could make it easier for heating installers, planners and architects to adapt the size and performance of a system to the requirements of buildings and end-users. In addition, some of the key stakeholders still lack the expertise to deal with the complex systems,” says Stieß.

Generally, the training and further education of heating installers is of particular importance. A training campaign is necessary so that innovative heat pump systems can be routinely planned, installed, commissioned and maintained in residential buildings. The critical shortage of skilled workers, however, makes training and further education measures even more difficult and is perceived as a major hurdle by the stakeholders interviewed.

Developing standardised solutions for better market acceptance

To improve market acceptance, the ISOE researchers recommend that heat pumps become more standardised and easier to install. Compact, space-saving systems or modules that are ready-made and can be easily combined with components from other manufacturers can increase the practicability and feasibility for both new and existing buildings. According to stakeholders and end-users, the equipment must be easy to install and operate. This is why combined packages, such as a heat pump with photovoltaics, intelligent control and thermal storage, are highly valued by investors and architects alike.

For buyers interested in heat pump systems, a clear application process to obtain funding is also considered important. In addition, there is a need for new financing and business models, such as heat contracting, to improve the market dissemination of innovative heat pump systems.

For more information about the project, please go to

Latest publication of the ISOE report:
Friedrich, Thomas/Immanuel Stieß (2021): Enhancing stakeholders' acceptance of trigeneration heating and cooling systems: Recommendations from the TRI-HP stakeholder process. Brussels: European Commission. 

Scientific contact:

Dr. Immanuel Stieß
Tel. +49 69 707 6919-19

Press contact:

Melanie Neugart
Tel. +49 69 707 6919-51