Modern vehicles with hybrid combustion-electric drive systems are an important element in the strategy for reducing fuel consumption and emissions of exhaust gas components. Determinant of the use and development is to achieve substantial benefits in terms of classical powertrain vehicles equipped with internal combustion engines. This paper presents the concept of kinematic ratio selection between the engine and the electric machine. This concept is based on the analysis of the internal combustion engine load caused by the resistances of motion and the best possible assessment of the additional load caused by the operation of the generator. It is proposed that the energy transferred to the generator was taken in a most preferred area of the engine performance characteristics and generator by changing kinematic ratio between the engine and the generator. The described concept can also be used for the recovery of vehicles braking energy.