The present patent application relates to a high-voltage motor vehicle electrical system comprising an electrical heating device and at least on further consumer during switching on of which, undesired electromagnetic oscillations may occur in the electrical system. According to the invention, these are suppressed by initially switching on the heating device, before the further consumer is switched on. Switching on the heating device changes the complete impedance of the electrical system such that a resonant enhancement of the interference oscillations is prevented. Preferably, the heating device is switched on only as shortly as possible (only during the switching on process of the further consumer) in order to minimize an undesired heating.