Abstract: A heating system for a room comprising two heat pumps. A base heat pump is designed so that its evaporator never freezes up or that no frost layer forms during wintertime operation. An auxiliary heat pump is provided and is put into operation during times of extreme cold, whenever the capacity of the base heat pump is not enough to sufficiently heat the room. When the outside heat exchanger of the auxiliary heat pump freezes up, provision is made to reverse the operation of the auxiliary heat pump so the outside heat exchanger becomes the condenser. Thus, the outside heat exchanger is thawed.