The heating of real estate and the warm service water for these required, be, through the use of energy, which is still in low solar radiation contain arrival, as far as possible thereby that the medium in one or more further energy store (n) with this low solar energy a water/water heat pump electrical Sole/water or electric powered, the, which shall be available to a higher temperature level transferred and a second heat generator. The second heat generator shall send this [...] -corresponding to the needs of the heating system and energy-if required, an under the warm water, regulated to this further. Advantages are : The low solar radiation can be used The groundwater wellbrine well and also should not be needed and therefore no the investment costs are low in a corresponding heating system. Even mining industry-legal permits are required no water-legally -or The the system can react on future developments in the energy market