 There is a variety of HEV types and the degree to which each function as an electric vehicle (EV) also varies.The most common form of HEV is the hybrid electric car, although hybrid electric trucks (pickups and tractors) and buses also exist.Modern HEVs make use of efficiency-improving technologies such as regenerative brakes which convert the vehicle's kinetic energy to electric energy, which is stored in a battery or supercapacitor.