Abstract: A heating/air-conditioning device includes a high-performance heat exchanger for providing air-conditioning of the vehicle cab of passenger cars and is designed and optimized for the large-scale production of passenger cars concerning quantity and costs. The construction size of a heat exchanger, which is already designed as a high-performance heat exchanger and has a soldered matrix, is enlarged beyond the previously known size, so that the vehicle delivers the same heating power as the previous basic series including a much more expensive PTC auxiliary heater. In addition to cost savings, fuel is saved in an order of 0.5-1.01/100 km, compared to an operation with a PTC auxiliary heater and at the same heating power.