A method is disclosed for supplying external energy to electrical on-board power networks of ships, with there being at least one generator, one converter and electrical loads in the ship's on-board power network. In at least one embodiment of the method, the converter (shore connection converter) on board the ship, for transfer into the on-board power network, is fed by a connectable external current source with current of a different frequency and voltage to that of the on-board network and the current is converted in the converter semiconductors into current with the voltage, and the frequency of the on-board power network and fed to the on-board power network.