If ground water is available and easily accessible, it can be utilized as a heat source due to the fact that it has a temperature of between 7 and 12 °C all-year round. It is advisable not to pump water for single and two-family houses from a depth greater than approximately 15 m. This would lead to expenditures being too high.

A distance of approximately 10 to 15 m should be kept between the withdrawal point (supply well) and the reinsertion point (deep-well) and furthermore the flow direction should be taken into consideration in order to avoid a “flow short-circuit”. These installations require a permit and must meet statutory requirements. However, this is no problem for NIBE equipment, due to their ISO 14001-certification. An optimal protection according to §7 MWG is provided by the “separator-exchanger-system”.