Uniform indications for electric consumers classifying are determined according to their technological signs and the physical forms of electrical energy conversion. Levels of consumption in electrical consumers are defined, on the basis of which 29 indexes for investigation, evaluation and comparison of the energy efficiency in electric drives are systematized. The indexes are distributed into 6 groups. Dependencies are defined and methods are developed for determination of the indexes system. An aggregate mathematical model for monitoring and evaluating the energy efficiency of grouped electric drives is synthesized. Case-study results for a typical belt-conveyor system in a thermo-electric power plant are obtained.