Abstract: A soil heat exchanger for effecting an energy exchange between earth soil and an energy exchanger and including a thermoinsulated flow duct arranged in a borehole formed in ground, a pump provided at an end of the flow duct, a shroud pipe surrounding the flow duct and the pump, and a return flow region for return water located radially outwardly of the shroud pipe and including return flow pipes and a porous filling, with the return flow pipe means extending down to a bottom of the borehole and having lateral opening means communicating with an interior of the shroud pipe through the inlet openings of the shroud pipe, with the shroud pipe having its lower end spaced from the bottom of the borehole, and with the lateral openings of the return flow pipes being beneath the lower end of the shroud pipe, and with the porous filling extending from the borehole bottom and at least up to a level above the inlet openings of the shroud pipe.