The invention relates to a system and method for supplying AC output power to at least one desired AC load. Values of electrical currents and/or voltages are measured by an energy measurement device within the system and an AC output power demand of the AC load is determined. An inverter unit inverts DC power received via the internal DC bus to AC power to supply AC output power to the connected AC load. The invention further comprises that the controller controls the electrical energy consumption of the inverter unit based on the AC output power demand.