Favoured by government subsidies, heat pumps are today’s most energy efficient heating and cooling systems in well-insulated buildings. They reduce the final energy demand by a factor of three and CO2 emissions by 25 to 65%. Heat pumps are mainly of interest for new buildings, since their integration often requires radical adaptations of the building’s design. This applies not only to the extraction of heat from the ground, ground water, or ambient air, but also to the distribution of heat. Heat pumps are best combined with low-temperature heating methods such as sub floor heating in well-insulated buildings. This is good news for contractors and electricians since their professional skills are indispensable.