Abstract: In order to optimize power supply costs and reduce billing rates in terms of prices charged per kilowatt-hour, the current consumed by a domestic installation is compared with a reference value and the result is transmitted to a microprocessor. As a function of this result, the microprocessor disconnects one or a number of power outputs in cascade and in a programmable order. In addition, the microprocessor receives a signal from one output of a relay which is responsive to rate-change data transmitted over the power distribution network at 175 Hz. When the billing rate is at a high price level, the microprocessor disconnects one or a number of outputs at the same time and as a function of a program established beforehand by the user.