 The heat drawn from ground-sourced systems is in most cases stored solar heat, and it should not be confused with direct geothermal heating, though the latter will contribute in some small measure to all heat in the ground.True geothermal heat, when used for heating, requires a circulation pump but no heat pump, since for this technology the ground temperature is higher than that of the space that is to be heated, so the technology relies only upon simple heat convection.Other heat sources for heat pumps include water; nearby streams and other natural water bodies have been used, and sometimes domestic waste water (via drain water heat recovery) which is often warmer than cold winter ambient temperatures (though still of lower temperature than the space to be heated).