The functionality of a heat pump is identical to that of a well-known everyday device: the refrigerator. The heat pump extracts the heat from the outside and releases it to the house as heating energy.
They are considered to be particularly climate-friendly, as they obtain "around three-quarters of the energy for heating from the environment" A prerequisite for the efficient use of heat pumps is very good thermal insulation of the building. Underfloor or wall heating systems in particular can be used well in combination with the heat pump for heating.