Autonomous operation of an energy supply device

An energy supply device contains: (a) a supply mechanism for supplying electrical power for a power supply system or for an electrical consumer connected to the power supply system; (b) a control unit for controlling an operation of the supply mechanism in first and second operating modes; (c) an interface configured to receive external control signals and to forward the external control signals that indicate how the supply mechanism works in the first operating mode; and (d) a communication monitoring unit that is coupled to the interface and the control unit and monitors whether external control signals are received by the interface, and, if the interface has not received any external control signals or any valid external control signals over a pre-determined amount of time, to transmit an operating mode control signal to the control unit, which causes it to operate the supply mechanism in the second operating mode.