The battery-only electric car is still a decade or more in the future (golf carts or "neighborhood electric vehicles"—limited to 35 mph—excepted), but plug-in hybrids can make a big difference soon. Like battery-only cars, plug-in hybrids have a battery that can be recharged from the electric grid. Like hybrids, plug-in hybrids also have a gasoline engine that can recharge the battery or power the vehicle. For short trips, electric grid energy stored in the battery is sufficient; no gasoline needs to be used at all. On longer trips the gasoline engine kicks in once the battery is significantly depleted.

Short trips are the key—70% of all trips are less than 15 miles. Since such a large percentage of normal use is for short trips, gasoline use can be cut dramatically even though the battery-only range is limited.

This page shows the numbers in detail, but the basic results for a 20-mile battery range are as follows: