To make it possible to reduce electric power consumption, by controlling in such a manner that transfer means is interrupted when a load factor based on the electric energy measured by electric energy measuring means exceeds a predetermined level.

A central arithmetic section 37 integrates signals depending on an electric energy transmitted from a power arithmetic section 34, determines the integrated watt-hour and outputs to a display section 38. Moreover, the central arithmetic section 37 determines load factor and, if this load factor exceeds a predetermined value, a switching control section 36 drives a switch gear 35 so as to open switches 35a and 35b, thereby creating an interrupted state between the conductor 33 and output terminals 32e, 32f and interrupting power supply to a controllable load 5. By doing this, the power consumption at the controllable lad can be reduced and, as a whole, the electric energy consumed can be reduced. Also, a possibility of exceeding the current limit predetermined by contract can be lowered and the power failure due to an excessive current consumption can be also prevented.