The heat pump, a proven and reliable technology, has the potential to reduce primary energy consumption and the corresponding CO2-emissions for heating and cooling in domestic, commercial and industrial applications. The basic principles of heat pump technology and the anthrogenic CO2-formation under the given energy supply and demand situation in Europe and the related impact on global warming are described. An analysis of the energy flow between primary energy exploitation and the useful energy of different heating systems clearly demonstrates the ability of electric heat pumps to reduce primary energy consumption in Europe between 15 and 50%, compared with oil- and gas-heating systems. The corresponding reduction of CO2-emissions will be between 20 and 60% and up to 85% of other pollutants. The present status of alternative working fluids which do not contribute to ozone depletion is presented and the direct (working fluids) and indirect (energy consumption) impact of different heat pumps on the greenhouse effect is discussed.