A method for operating a hybrid vehicle, the vehicle being driven by at least two power plants, and at least one electric power plant charging a high voltage energy system which supplies a low voltage energy system with electrical energy, a high voltage being converted into a low voltage for supplying at least one control unit of the vehicle, and the vehicle being disconnected from the electric power plant when a fault is detected in the high voltage system. To maintain the energy supply to the control units via the low voltage system even in the event of a fault in the high voltage system, the power plant is placed in a state for generating a voltage which is uncritical for the safety of the user after the high voltage system is disconnected, the safety-uncritical voltage being converted into the low voltage for supplying the at least one control unit.