Hybrid Electric Vehicle Basics

A hybrid electric vehicle uses an electric motor/generator along with an internal combustion engine—offering high fuel economy; low tailpipe emissions; and the power, range, and convenience of a conventional vehicle.

Cutaway diagram illustrating components of a hybrid electric vehicle. Components under the hood include (from the front of the vehicle) a thermal cooling system (rectangular flat box) adjacent to an auxiliary battery (small rectangular box), a DC/DC converter (rectangular box with fins), a power electronics controller (larger rectangular box), a transmission (not visible), a spark ignited internal combustion engine (large box) adjacent to an electric generator (cylinder with ridges) and electric traction motor (cylinder), and an exhaust system (pipes emanating from the engine area and continuing to rear of vehicle). Components toward the rear of the vehicle include a traction battery pack (large box), a gasoline fuel tank (larger box), and a fuel filler (fueling nozzle).

A hybrid electric vehicle does not plug in to charge. Instead, the battery is charged by the internal combustion engine and via regenerative braking.

In regenerative braking, the electric motor/generator captures energy normally lost during braking. This recovery and reuse of energy results in better fuel economy without sacrificing performance.

Energy stored in the battery provides extra power during starts and acceleration. It can also power auxiliary loads and reduce engine idling when the vehicle is stopped.

Additional Resources

Learn about NREL’s transportation research.

For more information about hybrid electric vehicles, visit the U.S. Department of Energy’s Alternative Fuels Data Center.