Cellars, particularly, are often heated passively and unintentionally. In some cases by boilers, in others by electrical appliances that give off large quantities of heat. Rather than allowing it to remain unused, the WWK heat pump reclaims this thermal energy. Equipped with a suitable fan, the hot water heat pump simply draws in the warm air and extracts any surplus thermal energy from it. The energy yielded as a result is then used to heat DHW. The intelligent energy management reclaims the latent heat for universal use, thereby reducing the energy costs. An entire detached house can be supplied with hot water by feeding the recovered heat into the integral cylinder. This way, modern heat pump technology can turn an apparent disadvantage into a real benefit.