In this paper a method is presented, which is used to configure an energy efficient powertrain of electric vehicles at an early stage of development. The method enables a loss estimation of the whole powertrain based on free accessible data sheets of the components. First of all, the main components in the powertrain are analysed. The analysis of the power losses will help to find those degrees of freedom for the powertrain design, which can influence the energy efficiency of the powertrain significantly. Subsequently, the powertrain will be dimensioned regarding the design requirements of electric vehicles. The degrees of freedom in the design lead to a number of powertrain configurations with different energy efficiencies. Finally, the configurations will be compared quantitatively regarding their energy efficiencies, which provides the basis for a fast selection of an energy efficient powertrain configuration.