Power from your brake pedal.

With Brake Energy Regeneration (available for the new BMW 7 Series), BMW EfficientDynamics points the way to a more energy-efficient future. As soon as you brake or take your foot off the accelerator, the kinetic energy is captured and fed to the battery. This reduces the amount of power the battery takes from the engine and hence lowers fuel consumption. When the driver presses the accelerator, on the other hand, the alternator is decoupled from the drivetrain. With fewer components drawing power from the drivetrain, more of the engine's output can go into accelerating the car.