A hybrid electric vehicle uses both an electric motor and an internal combustion engine to propel the vehicle.  A hybrid is designed to capture energy that is normally lost through braking and coasting to recharge the batteries (regenerative braking), which in turn powers the electric motor--without the need for plugging in.

A 'parallel' hybrid electric vehicle uses the electric motor or the internal combustion engine to propel the vehicle.  A 'series' hybrid electric vehicle uses the electric motor to provide added power to the internal combustion engine when it needs it most, for example, in stop-and-go driving and acceleration.  Hybrid electric vehicles have the potential to use electricity to power onboard accessories or to provide outlets to plug in appliances or tools.  All have the potential to achieve greater fuel economy than conventional gasoline-engine vehicles.

The hybrid market is growing--there are a variety of hybrid electric vehicles available to consumers today, with more models on the way.  Cities across the country are already benefiting from the use of hybrid electric buses in their communities.

Advantages of hybrids:
-Reduced fuel consumption and tailpipe emissions 
-Optimized fuel efficiency and performance
-Lower fueling costs
-Recovered energy from regenerative braking
-Uses existing gas station infrastructure

Challenges of hybrids:

-Complexity of two powertrains
-Component availability--batteries, powertrains, power electronics
-Higher initial cost