Free energy.

Brake Energy Regeneration in the
BMW 3 Series Sedan.

Until now, taking your foot off the accelerator meant that energy was going unused. However, thanks to BMW's Brake Energy Regeneration, this is no longer the case. The generator now transforms the vehicle's kinetic energy into electricity and uses this power to charge the battery. As a result, the battery's reliance on the engine is reduced - and so is fuel consumption.