In the near future, technical demands for powerful electric motors integrated into the drive train can be fulfilled. These motors combine the functionality of starter and alternator offering a higher electric power than conventional alternators. At low engine speed, they can work as a motor and introduce an additional driving torque in the drive train (booster). The required introduction of suitable electrical storage devices enables regenerative braking to reduce fuel consumption significantly. In this paper, for homologation tests and customer use, the potential savings of regenerative braking are shown for a variety of engines, vehicles and test cycles.