The invention relates to a method for heating the interior of a motor vehicle and to a heating system. In the method, electrical energy stored or generated in the motor vehicle or electrical energy supplied from an external energy source is supplied to an electrothermal converter and converted into thermal energy there, which is applied to a carrier medium for the thermal energy. An electrothermalconverter that is briefly operated with a higher heating power in the heat-up phase than in the subsequent continuous operation is used. In this way, the motor vehicle interior can be heated up considerably faster than in the case of known methods.