Abstract: An energy supply device for supplying electric loads with electric energy, includes a DC link; a first mains connection to which a first AC voltage grid can be connected as intended; a first rectifier which is designed to rectify an AC voltage corresponding to an AC voltage across the first mains connection or based thereon and to feed the rectified voltage into the DC link; a second mains connection to which a second AC voltage grid can be connected as intended; a second rectifier which is designed to rectify an AC voltage corresponding to an AC voltage across the second mains connection or based thereon; a controllable DC-to-DC converter to a first side of which a voltage rectified by means of the second rectifier is applied, and a second side of which is connected to the DC link; a first current converter which is fed from the DC link and is designed to supply a first electric load with electric energy; a power measuring apparatus which is designed to measure electric power consumed at the first mains conn