An apparatus has an input section arranged to receive values representative of the total instantaneous supply of electrical current as a function of time from an alternating voltage supply. Current waveforms comprising sets of values representative of the cyclic waveform of the electric current supply are obtained. A delta waveform generator calculates the difference between a current waveform and an earlier current waveform. An edge detector is arranged to detect an edge or edges in the delta waveform. An analysis section is arranged to identify at least one appliance load based at least on information on the edge or edges detected by the edge detector, and to determine the electrical energy consumed by said appliance load.