Heat pumps are the most common heat generators in new buildings in Switzerland today. Even in existing buildings, more and more heat pumps are being installed. The aim of the 4-year project is to limit the power consumption of heat pumps with geothermal energy (borehole heat exchanger). The annual performance factor should be increased by 20 percent compared to the current state of the art. Considering the many plants and the prognosis that hundreds of thousands of such plants will be built in the next 20 years, this is of great importance.