Heat pump technology has already won the direct comparison with conventional heating processes. It allows the use of freely available energy, regardless of dwindling resources, and consumes little power.
The COP value (coefficient of performance) - which indicates the ratio of heat output (kW) to the amount of electrical energy input (kW) - is used as standard of efficiency.
This value, however, is relatively inaccurate because it does not allow for the large temperature change spread over the course of the year. To determine the efficiency under consideration of all factors, the annual energy efficiency ratio (AEER) must be measured.
An annual energy efficiency ratio of 3, for instance, means that three times the electrical efficiency applied is converted into heat energy. The consumption data can be used to draw conclusions about generation of emissions. For this reason, the AEER is also used as standard for state-sponsored heat pump promotions.
The actual AEER depends on four additional factors: applied heat pump technology, home insulation or installation, outside temperature, as well as user behaviour. Thus, windows that remain open during cold winter days or poorly insulated exterior walls reduce the AEER, i.e. the overall efficiency.