Plug-in hybrids, sometimes called Plug-in Hybrid-Electric Vehicles (PHEVs), are hybrids with high-capacity batteries that can be charged by plugging them into an electrical outlet or charging station. They can store enough electricity from the power grid to significantly reduce their petroleum consumption under typical driving conditions.
Different Kinds of Plug-in Hybrids
There are two basic plug-in hybrid configurations:
Series plug-in hybrids, also called Extended Range Electric Vehicles (EREVs). Only the electric motor turns the wheels; the gasoline engine is only used to generate electricity. Series plug-ins can run solely on electricity until the battery needs to be recharged. The gasoline engine then generates electricity to power the electric motor. For shorter trips, these vehicles might use no gasoline at all.
Parallel or Blended Plug-in Hybrids. Both the engine and electric motor are mechanically connected to the wheels, and both propel the vehicle under most driving conditions. Electric-only operation usually occurs only at low speeds.
Plug-in hybrids also have different battery capacities, allowing some to travel farther on electricity than others. Their fuel economy, like that of electric vehicles and regular hybrids, can be sensitive to driving style, driving conditions, and accessory use.
Benefits and Challenges
Less Petroleum Use. Plug-in hybrids use roughly 30% to 60% less petroleum than conventional vehicles. Since electricity is produced mostly from domestic resources, plug-in hybrids reduce oil dependence.
Less Greenhouse Gas Emissions. Plug-in hybrids typically emit less greenhouse gas than conventional vehicles, but the amount generated depends partly on the fuel used at electrical power plants—nuclear and hydroelectric plants are cleaner than coal-fired power plants.
Higher Vehicle Costs, Lower Fuel Costs. A plug-in hybrid can cost roughly $4 to $8 thousand more than a comparable non-plug-in hybrid. Using electricity is usually cheaper than using gasoline—sometimes much cheaper—but whether fuel savings will offset the higher vehicle cost depends on the vehicle purchased, the percentage of miles operating on electricity, fuel costs, and ownership length. Federal tax incentives up to $7,500 are currently available for qualifying plug-ins.
Re-charging Takes Time. Re-charging the battery using a 120-volt household outlet can take several hours; re-charging using a 240-volt home or public charger can take roughly 1 to 4 hours; while a "fast charge" to 80% capacity may take as little as 30 minutes. However, these vehicles don't have to be plugged in. They can be fueled solely with gasoline but will not achieve maximum range or fuel economy without charging.
Estimating Fuel Economy. Since a plug-in can operate on electricity alone, gasoline alone, or a mixture of the two, EPA provides a fuel economy estimate for gasoline-only operation and an estimate for electric-only or gas-and-electric operation—both for combined city-highway driving.