The research concerns railway transport and devoted to the analysis of heating processes during the testing of the heating of dynamoelectric machines of rolling stock. The aim of the research is the decrease of power consumption for the after-repair acceptable tests of dynamoelectric machines by optimization of loading conditions. The estimation method of power efficiency of heating tests with the help of the index is suggested in the work. It represents the power relation, expended for the temperature increase of armature coil of electric machine, and the relation to the full loss in armature during the testing. The result of the differential equation of armature coil heating was the analytical formula for determination of the coefficient of the heating power efficiency according to the thermal parameters of the tested electric machine. To decrease the total power expenditure it was suggested to hold the test at load current higher than the watch value. It was shown that the increase of load current of tested electric machines to starting value helps to decrease total costs in their armatures almost one and a half time in comparison with the watch mode.