A system with an internal combustion engine which has a heat transfer circuit, a fuel cell and a climate control unit which is accommodated in the heat transfer circuit of the internal combustion engine. The system has a heat transfer arrangement for transferring the exhaust heat of the fuel cell to the heat transfer circuit and a bypass for bridging a segment of the heat transfer circuit which runs through the internal combustion engine so that, in the bypassed operating state, an isolated circuit is formed. In stationary operation, this enables an optimized operating mode since the internal combustion engine is no longer heated and the exhaust heat of the fuel cell is fully available for heating purposes. The climate control unit can have a fuel cell and an arrangement for transferring the heat produced by the fuel cell to the vehicle interior has a fan unit by which an air flow can be produced for cooling the fuel cell and a heating unit which is powered by the fuel cell and by which the air flow for heating the vehicle interior can be additionally heated. For cooling or heating the interior of a motor vehicle, the system can have a cooling circuit with a compressor, a condenser, an expansion element, and a first evaporator and an APU or a fuel cell to electrically power the compressor, and a second cooling circuit a second evaporator, the second cooling circuit being connected to the first cooling circuit.