A system for measuring power in an electrical distribution circuit having at least three wires includes a Hall-effect generator directly coupled to one of the live wires of the circuit and current transformers coupled to the other live wires of the circuit. The output of each current transformer is magnetically linked to the Hall-effect generator. The excitation current for the Hall-effect generator is derived from the line potential between the live wires. The Hall-effect generator acts to produce an output whose magnitude is directly proportional to the product of the vector sums of the currents flowing in the live wires and the potential between the live wires. This power indicative output may be accumulated to produce an indication of energy consumed by a load connected to the live wires. A high frequency A.C. bias is applied to the Hall generator in order to linearize the output of the generator.