Skip Navigation to main content U.S. Department of Energy Energy Efficiency and Renewable Energy
Alternative Fuels and Advanced Vehicles Data Center
About the AFDCFuelsVehiclesFleetsIncentives and LawsData, Analysis and TrendsInformation ResourcesHome
Alternative and Advanced Vehicles

What is a hybrid electric vehicle?

Hybrid electric vehicles (HEVs) typically combine the internal combustion engine of a conventional vehicle with the battery and electric motor of an electric vehicle. The combination offers low emissions, with the power, range, and convenient fueling of conventional (gasoline and diesel) vehicles—and HEVs never need to be plugged in.

Hybrid electric vehicles of the future could use alternative fuels such as biodiesel, natural gas, or ethanol. The flexibility of HEVs makes them well suited for fleet and personal transportation. Learn more about the components of a hybrid system.

Hybrid electric vehicles were not included as qualified alternative fuel vehicles under the Energy Policy Act of 1992. The National Defense Authorization Act for Fiscal Year 2008 amended the Energy Policy Act of 1992 and classified several new vehicles as "alternative fueled vehicles" (AFV) as defined in Section 30B of the Internal Revenue Service (IRS) Code. The four new categories of vehicles include:

  • A new qualified fuel cell motor vehicle
  • Advanced lean-burn engine technology motor vehicle
  • A new qualified hybrid motor vehicle
  • Any other type of vehicle that the Administrator of EPA demonstrates to the Secretary of Energy would achieve a significant reduction in petroleum consumption.

HEVs qualify for incentives and provide several important benefits. Learn about currently available HEVs.

How Hybrid Electric Vehicles Work

Hybrid electric vehicles are powered by two energy sources—an energy conversion unit (such as an internal combustion engine or fuel cell) and an energy storage device (such as batteries or ultracapacitors). The energy conversion unit can be powered by gasoline, diesel, compressed natural gas, hydrogen, or other fuels.

Hybrid electric vehicles have the potential to be two to three times more fuel-efficient than conventional vehicles. HEVs can have a parallel design, a series design, or a combination of the two.

View an animation showing how HEVs work. (Download Flash Player.) Or view the text version.

Schematic of a hybrid electric vehicle showing the arrangement of the internal combustion engine, generator, power split device, electric motor, and battery. The schematic links to a U.S. Department of Energy/Environmental Protection Agency fueleconomy.gov animation and text description of the schematic.

This animation shows how HEVs work.
(Source: FuelEconomy.gov)