Air conditioning apparatus during vehicle stop

The heating system (1) for a truck to be used when it is at rest, where the driver's cab is also used for sleeping quarters, has a heat pump circuit (2) with a heat transfer unit (3) to take up environmental heat from an ambient air inflow (15) and a second heat exchanger (4) to deliver heat into the vehicle interior (16). A compressor (5), with an electrical or mechanical drive (6), is in the circuit between the heat exchangers. An additional heat exchanger (8) transfers heat from the electrical/mechanical drive to the heat pump circuit.