What is a plug-in hybrid electric vehicle?

Plug-in hybrid electric vehicles (PHEVs) can be charged with electricity like pure electric vehicles and run under engine power like hybrid electric vehicles. The combination offers increased driving range with potentially large fuel and cost savings, emissions reductions, and other benefits.

Plug-in hybrid electric vehicles currently do not qualify as alternative fuel vehicles under the Energy Policy Act of 1992. However, they do qualify for incentives.

Plug-in hybrid electric vehicles are still at a pre-commercial stage of development. Research and development efforts are bringing them closer to widespread commercialization.

How Plug-in Hybrid Electric Vehicles Work

Like hybrid electric vehicles, PHEVs are powered by two energy sources—an energy conversion unit (such as an internal combustion engine or fuel cell) and an energy storage device (usually batteries).

The energy conversion unit can be powered by gasoline, diesel, compressed natural gas, hydrogen, or other fuels. The batteries can be charged by plugging into a standard 110-volt electrical outlet—a capability conventional hybrid electric vehicles do not have—in addition to being charged by the energy conversion unit when needed.

Plug-in hybrid electric vehicles have a larger battery pack than conventional hybrid electric vehicles. During typical daily driving, most of a PHEV's power comes from the stored electricity. For example, a 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 in the morning. However, the engine can be used when longer trips are required, and the PHEV does not need to be plugged in to operate.

Vehicle-to-Grid Concept

Researchers are developing "vehicle-to-grid" technologies that allow a two-way connection between the plug-in hybrid electric vehicle and the local utility grid. While the vehicle is plugged in and not in use, the utility could take advantage of the extra electrical storage capacity in the vehicle batteries to help meet peak electricity demand, provide grid support services, or respond to power outages. PHEV owners could get "paid" by the utility for use of their vehicles, which would only be used when needed and without negative effects on the vehicle battery's state of charge.