Electric Power Steering.
The Electric Power Steering only activates when it’s needed: when you're turning the wheel. The energy it requires has previously been extracted by Brake Energy Regeneration from the braking and kinetic energy.
This element of BMW EfficientDynamics replaces the conventional hydraulic power-steering system with an electric motor. While hydraulic systems constantly draw power from the engine – thereby consuming extra fuel – the innovative BMW system only springs into action when it's actually needed. If you don't move the steering wheel (on a straight, for example, or on a steady curve) the electric motor remains inactive, reducing power consumption.