A hybrid electric vehicle (HEV) is a vehicle that uses two or more distinct power sources to propel the vehicle such as:

* An on-board rechargeable energy storage system (RESS) and a fueled power source (internal combustion engine or fuel cell) for vehicle propulsion * Air and internal combustion engines; it is also called a bi-energy vehicle. * Human powered bicycle with electric motor or gas engine assist * A human-powered or sail boat with electric power.

The term most commonly refers to Hybrid-electric vehicle (HEV) which includes internal combustion engines and electric motors (generally powered by electric batteries, other rechargeable energy storage system -RESS- or overhead wires).

The hybrid vehicle typically achieves greater fuel economy and lower emissions than conventional internal combustion engine vehicles (ICEVs), resulting in fewer emissions being generated. These savings are primarily achieved by four elements of a typical hybrid design: 1) recapturing energy normally wasted during braking etc.; 2) having significant battery storage capacity to store and reuse recaptured energy; 3) shutting down the gasoline or diesel engine during traffic stops or while coasting or other idle periods; 4) relying on both the gasoline (or diesel engine) and the electric motors for peak power needs resulting in a smaller gasoline or diesel engine sized more for average usage rather than peak power usage. These features make a hybrid vehicle particularly efficient for city traffic where there are frequent stops, coasting and idling periods. In addition noise emissions are reduced, particularly at idling and low operating speeds,[1] in comparison to conventional gasoline or diesel powered engine vehicles. For continuous high speed highway use these features are much less useful in reducing emissions. Vehicles which have significant idle periods and only occasional needs of peak power like railroad switching locomotives or repeated lifting and lowering cycles like Rubber Tyred Gantrys are also good candidates for hybrid systems resulting in potentially significant fuel and emission savings.

All major auto manufacturers produces hybrid vehicles. The Toyota Prius is the number-one selling hybrid car at 46 mpg. The following is a list of popular hybrid models:

Toyota Prius
Honda Civic Hybrid
Nissan Altima Hybrid
Toyota Camry Hybrid
Ford Escape Hybrid
Mercury Mariner Hybrid
Lexus RX 400h
Toyota Highlander Hybrid
Lexus GX 450h
Cherolet Tahoe Hybrid
Lexus LS 600h L
Hyundai Accent Hybrid
BMW X6 Hybrid
Porsche Cayenne Hybrid
Honda Global Subcompact Hybrid
Ford Reflex
Mercury Meta One
Toyota Volta
Toyota Sienna Hybrid
Toyota Hybrid X
Saab BioPower Hybrid
Volvo 3CCC
Toyota A-BAT Concept Hybrid Pickup Truck
Honda Insight
Honda Accord Hybrid