This paper shows a methodology for assessment and optimization of induction electric motors aiming energy conservation, through substitution of older electric motors by high-efficiency ones, including motor resizing, aided by computer simulation. Energy Diagnosis aims to provide the client with a decrease in electric energy costs, not only a decrease in demand, but as well as a decrease in consumption. This study and its application were carried out through the Electric Energy Efficiency Program promoted by the Brazilian Electric Energy Agency. These programs, which can be financed by the utilities, arouse the interest for the implementation of energy efficiency projects. Once the electric motor is an equipment of final use strongly present at industry, it is subject to new substitution, bringing satisfactory results when the diagnosis is carried out in a consistent way and following coherent procedures for its validation. The methodology adopted for the substitution of these motors included an initial study, by means of measurements of electrical parameters, through the use of a power quality analyzer. Afterwards, by using a particular simulation software, the operating conditions of the electric motor and the expected economy obtained by the use of high-efficiency motors were estimated. When necessary, the motor resizing analysis provides the best rated power for the drive. The motor substitutions carried out in this motor drives efficiency improvement program resulted in yearly savings of 3.1 GWh, equivalent to 4.52% of the previously required energy.