How much electricity from the grid is required can be directly influenced by the size of the PV system. This is easily possible for energy-saving detached houses with, for example, 10 kWp PV. In addition, a heat pump can "only" generate heat. There is no contribution to the electrical consumers in the building. In contrast, photovoltaics gives priority to normal household electrical consumers before heat generation and thus contributes to the reduction of operating costs to the highest degree.