Plug-in hybrids can run in full-electric mode from electricity stored in their battery packs. For example, the Chevy Volt can go up to 40 miles on electricity alone. Plug-in hybrids like the Volt come with a 120-volt portable charging cord and can be fully charged in most traditional outlets in about 10 hours. These hybrids can also be charged at more efficient, 240-volt public or home-installed stations in about four hours.
When running on gas, plug-in hybrids are still efficient - the Volt gets about 37 mpg - but in full EV mode, gas mileage can be phenomenal. The Volt, for example, can get the equivalent of 94 mpg.
Although plug-in hybrids are generally more expensive and less common than traditional hybrids, they are excellent options if you're looking for a way to get better gas mileage and lessen your impact on the environment.