Hybrid electric vehicles combine features of internal combustion engines (using gasoline, diesel, natural gas, ethanol or other fuel) and electric motors. Unlike 100 percent electric vehicles, hybrid vehicles do not need to be plugged into an external source of electricity to be recharged; most operate on gasoline.

 

Hybrid passenger cars arrived in the U.S. in model year 2000, following their introduction in Japan a few years earlier. First came the two-seat Honda Insight, followed by the Toyota Prius in model year 2001. They are now available in many makes and models.

 

Hybrid systems have also proved effective in buses and heavy trucks, including military vehicles, transit buses and many others. (Source: EPA, NREL / Photo: Flickr)