Borehole heat exchangers are used to extract heat stored in the ground by means of a vertical borehole with a “closed loop” collector installation with the help of a geothermal heat pump. A collector hose filled with a carrier fluid is installed in the borehole which is drilled into a geothermal aquifer. This circulating carrier fluid absorbs heat from the surrounding bedrock, which is then extracted by the heat pump for use in space-heating via piping connected to the heat exchanger.