Abstract: A heat pump assembly comprises a refrigeration circuit including an evaporator, a compressor and a capacitor, and an internal combustion engine for driving the compressor and being coupled therewith by a detachable coupling. A heating circuit is disposed in communication with the capacitor and includes a space heat exchanger for the heating of space by heat absorbed from the capacitor, and further includes the engine, a heat exchanger in a communication with an exhaust pipe extending from the engine, and a retarder driven by the engine for the torque loading of same. Space is thus further heated by the engine and the emissions therefrom, and the retarder comprises an electric braking arrangement by which energy to be dissipated is converted into heat by eddy currents produced in a solid conductor.