Abstract: In a power control system for motor vehicles with a plurality of power-converting elements as well as sensors for determining the efficiency of the individual elements, a processor determines the overall system efficiency from the efficiencies of the individual components, and calculates and adjusts a value for a parameter that influences the efficiency of at least one component to achieve an optimum total efficiency. Surplus power is used to charge an energy storage device. Preferably the parameters that influence the efficiency, whose values are adjusted to achieve an optimum total efficiency, are the power, or a parameter that is proportional to the power, that is to be delivered by a power-generating component, and/or the rpm or a parameter that is proportional to the rpm of a component.