Those in search of emission-free electric driving currently have two options to choose from: hydrogen fuel-cell electric vehicles (HFCVs or FCEVs) and battery-electric vehicles (BEVs). Once enough of the battery's energy is drained, PHEVs rely on the gasoline engine to serve as a generator and/or power source for the drive wheels. PHEVs allow for short-range operation on battery power alone. Plug-in-hybrid vehicles (PHEVs) take this same concept and add the option to pull power from an external source, such as the energy grid itself, courtesy of an external charge port. A hybrid, such as the Toyota Prius, burns fossil fuel to power the vehicle's internal-combustion engine, which subsequently plays a part in generating the electricity needed to power the car's electric drive motor (an onboard battery pack stores this energy).
