A power system includes at least one generator driven by at least one of a number (N) of prime movers, at least one energy storage device, and at least one control device, wherein the generator and the energy storage device provide electrical energy to a power grid having an external load. The power system includes at least one first measuring device for determining at least one first signal for a computer to determine what amount of electrical power (ΣPG,i) has to be generated by the at least one generator to meet a power requirement (Pload) of the external load. The at least one control device is configured to receive the at least one first signal and to influence the control of the speed (ni) of the at least one of the number (N) of prime movers or the frequency (f) of the power grid taking into account the at least one signal to change the mechanical power generated by the at least one of the number (N) of prime movers such that the electrical power provided by the at least one generator approaches the power requirement (Pload) of the external load in situations where the power requirement (Pload) of the external load is at least partially provided for by the at least one energy storage device.