Plug-In Hybrid Electric Vehicle Basics
Animation of a vehicle with a battery, electric motor, and internal combustion engine inside and icons depicting electrical power and conventional or alternative fuel outside.
Plug It in or Fill It Up
Plug-in hybrid electric vehicles have an internal combustion engine and electric motor. These vehicles are powered by an alternative fuel or a conventional fuel, such as gasoline, and a battery, which you can plug in to charge.
Plug-in hybrid electric vehicles (PHEVs) are powered by conventional or alternative fuels and by electrical energy stored in a battery. Using electricity from the grid to run the vehicle some of the time costs less and reduces petroleum consumption compared with conventional vehicles. PHEVs might also reduce emissions, depending on the electricity source.
Heavy-duty vehicles can be converted to PHEVs and a few light-duty PHEVs are commercially available. Although PHEVs will likely be more expensive than similar conventional and hybrid vehicles, some cost can be recovered through fuel savings, a federal tax credit, or state incentives.
Powered by Electric Motor and Engine
Plug-in hybrid electric vehicles have an internal combustion engine or other propulsion source and an electric motor, which uses energy stored in batteries. PHEVs have a larger battery pack than hybrid electric vehicles. This makes it possible to drive for an extended range using just electricity (about 10 to 40 miles in current models), commonly referred to as the "all-electric range" of the vehicle.
During urban driving, most of a PHEV's power comes from stored electricity. For example, a light-duty PHEV driver might drive to and from work on all-electric power, plug in the vehicle to charge it at night, and be ready for another all-electric commute the next day. For longer trips or periods of higher acceleration, the internal combustion engine is used. Heavy-duty PHEVs can work somewhat differently, using the internal combustion engine while a worker drives to and from a job site and using electricity to power the vehicle's equipment or to keep the vehicle's cab at a comfortable temperature at the job site.
Fueling and Driving Options
Plug-in hybrid electric vehicle batteries can be charged by an outside electric power source, by the internal combustion engine, or through regenerative braking. During braking, the electric motor acts as a generator, using the energy to charge the battery. Learn more about charging PHEVs.
PHEV fuel consumption depends on the distance driven between battery charges. For example, if the vehicle is never plugged in to charge, fuel economy will be about the same as a similarly sized hybrid electric vehicle. If the vehicle is driven less than its all-electric range and plugged in, it may be possible to use only electric power.
Fuel-Efficient System Design
Beyond battery storage and motor power, there are various designs for combining the power from the electric motor and the engine. The two main designs are parallel and series.
Parallel plug-in hybrids connect the engine and the electric motor to the wheels through mechanical coupling. Both the electric motor and the engine can drive the wheels directly.
Series plug-in hybrids use only the electric motor to drive the wheels. The internal combustion engine is used to generate electricity for the motor. General Motors (GM) uses a slightly modified version of this design in the Chevy Volt. GM refers to this design as an extended range electric vehicle (EREV). In an EREV, the electric motor drives the wheels almost all of the time, but the vehicle can switch to work like a parallel hybrid at highway speeds when the battery is depleted.