Energy  can  be  created  nor  be  destroyed. just,  it  can   be  converted  from  one  form  to  another . Taking large amounts of heat energy is lost to the atmosphere during.  It  will  be  good  if  it  can  store  this  energy  somehow  which  is  otherwise  getting  wasted out  and   it  next time  we  started  to  accelerate.  During regenerative braking, slowing the vehicle's kinetic energy, the accumulated energy, refers to a system that is temporarily stored and used again as kinetic energy during acceleration or operation.  Regenerative  braking  is  a  small,  yet  very  important,  step  toward  our  eventual  independence  from fossil  fuels. These  brakes  allow  batteries  to  be  used  for  longer periods  of  time  without  the  need  to  be  plugged  into  an  external  charger. It  types  of  brakes  also  extend  the  driving  range  of  fully  electric vehicles.  Regenerative braking  is  a  way  to  extend  range  of  the  electric vehicles.  In many cases, hybrid vehicles, this system also applies to hybrid vehicles improve fuel economy.Normal  car  is  just  about 20%  efficient,  meaning  some  80%  of  the  energy  it  expends  is  wasted  as heat  created  by  friction.

Regenerative braking we mobilize more fuel to create heat which is produced by using fuel instead of paying equals wasted energy is wasted to the environment, you can get back up to half