Technical Highlights

Plug-in Hybrid Electric Vehicles 

Traditional hybrid vehicles are powered by both an internal combustion engine and a rechargeable battery, yielding fuel economy 

improvements up to 30-60 percent over conventional gasoline-only 

models. Plug-in hybrid vehicles come with the added feature of a plug 

that allows the vehicle to be recharged through a conventional electrical outlet. 

This fact sheet describes the benefits and costs of plug-in hybrids. It 

also provides information about their future development as well as 

State and local policies to encourage their use. 

Plug-in hybrids can reduce oil use and greenhouse gas 

emissions and promote development of advanced vehicle 

technologies. 

By shifting the automobile’s energy source from conventional fuels to electricity, 

plug-in hybrids offer potential for a number of environmental and energy security 

benefits, such as: 

•	 Reducing U.S. consumption of petroleum; 

•	 Reducing greenhouse gas emissions; and 

•	 Advancing battery and other technologies that could ultimately make 100% 

electric vehicles commercially viable. 

Much of the current interest in plug-in hybrids arises from their key role in scenarios 

to stabilize the accumulation of transportation-related greenhouse gasses in the 

atmosphere. A recent EPA analysis found that if plug-in hybrids had a 30% market 

share by 2025 (and maintained it until 2050) they could reduce emissions of up 

to 11,000 million metric tons (MMT) of CO2 from now to 2050 (see “A Wedge 

Analysis of the U.S. Transportation Sector” [insert hyperlink]). This is roughly a 

quarter of the 45,000 MMT of CO2 that analysts estimate would have to be reduced 

by 2050 to stabilize emissions from the entire transportation sector (including trucks, 

aviation, rail, and other sources in addition to passenger cars). 

The amount of greenhouse gas emissions reduced by plug-in hybrids depends upon 

the source of the electricity used to charge the vehicle when it is plugged in. For 

example, plug-in hybrids charging with electricity generated from burning coal would 

be responsible for more greenhouse gas emissions than those charging with electricity 

Office of Transportation and Air Quality 

EPA420-F-07-048 

October 2007 
Technical Highlights

from a renewable source, such as wind. Current studies have found that even plug-in hybrids 

using current electricity generation sources are responsible for fewer greenhouse gas emissions 

than conventional gasoline vehicles. 

Future developments are likely to improve the cost-effectiveness of 

plug-in hybrids. 

Plug-in hybrids have a larger up-front cost than current hybrid vehicles because of their larger 

battery, motors, and power electronics. However, fuel costs are lower for plug-in hybrids because 

per-mile electricity costs are lower than those for gasoline. This is especially true in areas where 

electricity rates are lower at night when most plug-in hybrids will be recharged. 

Over time, research and mass production will likely improve the cost-effectiveness of plug-in 

hybrids. A number of universities, federal agencies, research organizations, utility companies, 

battery companies, and automakers are researching advances in plug-in hybrid technology. For 

example, the National Renewable Energy Laboratory (NREL) and several other organizations 

are seeking lighter weight, less expensive energy storage technologies. While plug-in hybrids 

are currently produced through conversion kits for traditional hybrid vehicles, General Motors 

recently announced plans to go into mass production of the first commercially available plug-in 

hybrid--the Saturn Vue and Chevy Volt. 

State and local policies are encouraging the use and development of 

plug-in hybrids. 

State and local governments have pursued a number of initiatives to promote the use of plug-in 

hybrids, including: 

•	 A state law in Minnesota that encourages the State to buy plug-in hybrids for its public 

fleets; 

•	 Demonstration projects in New York and California to analyze the feasibility and 

environmental benefits of introducing plug-in hybrids; 

•	 A sales tax rebate in South Carolina for the private purchase of plug-in hybrids; and 

•	 The “Plug-in Partners” initiative by the municipal electric utility in Austin, Texas to 

seek commitments from U.S. cities and utilities to help create a market for plug-in 

hybrids. 

Where can I go for additional information? 

You can access additional information about the characteristics of plug-in hybrids at the 

following web sites: 

•	 A New Type of HEV: The Plug-in Hybrid (Department of Energy): 

www.eere.energy.gov/afdc/vehicles/hybrid_electric.html 

•	 Plug-in Hybrid Web Page (DOE National Renewable Energy Laboratory): 

www.nrel.gov/vehiclesandfuels/hev/plugins.html 

•	 State Clean Energy-Environment Technical Forum on Plug-in Hybrid Vehicles 

(Environmental Protection Agency and Keystone Institute, see March 15, 2007 forum): 

www.keystone.org/html/documents.html 

Plug-in Hybrid Electric Vehicles