KERS is one of the application of regenerative braking. Regenerative Braking converts some of the waste heat energy produced during braking into more useful form of energy with the help of MGU (Motor Generator Unit). The system stores the energy in a battery (after applying brakes) produced under breaking in a reservoir and then releases the stored energy under acceleration. The key purpose of the introduction is to significantly reuse the wasted energy in some application of cars. KERS is introduced to improve fuel efficiency of the engine.