This CO2 heat pump functions in the same way as a heat pump with conventional refrigerants. By using CO2 as a refrigerant, the heat pump can operate much more efficiently in a high temperature range and performs more efficiently at low ambient temperatures. Due to the maximum outlet temperature of 90°C, the CO2 heat pumps can be used for the production of domestic hot water. The CO2 heat pump in combination with buffer tanks can also be used to replace existing gas boilers for space heating. Existing central heating installations often require a minimum supply temperature of 80°C. The CO2 heat pumps are therefore an excellent device to make existing buildings more sustainable. The CO2 heat pumps are suitable for collective heating in apartment buildings, small district heating systems, sanitary hot water production for swimming pools, sports accommodations, hotels and holiday parks. By combining the central heating system with hot water production, the Seasonal Performance Factor (SPF) becomes even better.