Combination of heat recovery system and APU assembly

The unit has an internal combustion engine (1) coupled to an output shaft, and a waste heat utilization system (5) for converting part of waste heat from an exhaust gas system (10) into electrical energy by a thermally operated energy converter. The electrical energy is supplied partly to auxiliary equipments and/or an electrical onboard network of a motor vehicle. A heat source (2) is additionally provided to the waste heat utilization system for providing heat to the energy converter, where the converter has an expansion machine (4).