Electrical power supply device intended to supply power to an electrical appliance in a building or conglomeration, the which device incorporates: - an AC voltage input; - an DC power outlet; - a voltage converter able to transform the AC voltage at the input into a DC voltage; and - a control system able to interrupt the operation of the voltage converter; in which: - the device also incorporates: ▪ an energy storage system; and ▪ an internal DC voltage network connected to the energy storage system, to the outlet and to the voltage converter's DC voltage; - and the control system is able to: ▪ detect a charge (Ec) status of the energy storage system; ▪ measure a current (Is) coming from the DC power outlet; ▪ interrupt the operation of the voltage converter when it detects that the current (Is) coming from the DC power outlet is less than a first threshold value; ▪ activate the operation of the voltage converter when it detects the charge (Ec) of the energy storage system is less than a second threshold value; and ▪ interrupt the operation of the voltage converter when it detects that the charge (Ec) of the energy storage system is greater than a third threshold value. - an AC voltage input; - an DC power outlet; - a voltage converter able to transform the AC voltage at the input into a DC voltage; and - a control system able to interrupt the operation of the voltage converter; in which: - the device also incorporates: ▪ an energy storage system; and ▪ an internal DC voltage network connected to the energy storage system, to the outlet and to the voltage converter's DC voltage; - and the control system is able to: ▪ detect a charge (Ec) status of the energy storage system; ▪ measure a current (Is) coming from the DC power outlet; ▪ interrupt the operation of the voltage converter when it detects that the current (Is) coming from the DC power outlet is less than a first threshold value; ▪ activate the operation of the voltage converter when it detects the charge (Ec) of the energy storage system is less than a second threshold value; and ▪ interrupt the operation of the voltage converter when it detects that the charge (Ec) of the energy storage system is greater than a third threshold value. - the device also incorporates: ▪ an energy storage system; and ▪ an internal DC voltage network connected to the energy storage system, to the outlet and to the voltage converter's DC voltage; ▪ an energy storage system; and ▪ an internal DC voltage network connected to the energy storage system, to the outlet and to the voltage converter's DC voltage; - and the control system is able to: ▪ detect a charge (Ec) status of the energy storage system; ▪ measure a current (Is) coming from the DC power outlet; ▪ interrupt the operation of the voltage converter when it detects that the current (Is) coming from the DC power outlet is less than a first threshold value; ▪ activate the operation of the voltage converter when it detects the charge (Ec) of the energy storage system is less than a second threshold value; and ▪ interrupt the operation of the voltage converter when it detects that the charge (Ec) of the energy storage system is greater than a third threshold value. ▪ detect a charge (Ec) status of the energy storage system; ▪ measure a current (Is) coming from the DC power outlet; ▪ interrupt the operation of the voltage converter when it detects that the current (Is) coming from the DC power outlet is less than a first threshold value; ▪ activate the operation of the voltage converter when it detects the charge (Ec) of the energy storage system is less than a second threshold value; and ▪ interrupt the operation of the voltage converter when it detects that the charge (Ec) of the energy storage system is greater than a third threshold value.