Many people have probably owned a hybrid vehicle at some point. For example, a mo-ped (a motorized pedal bike) is a type of hybrid because it combines the power of a gasoline engine with the pedal power of its rider. In fact, hybrid vehicles are all around us. Most of the locomotives we see pulling trains are diesel-electric hybrids. Cities like Seattle have diesel-electric buses -- these can draw electric power from overhead wires or run on diesel when they are away from the wires. Giant mining trucks are often diesel-electric hybrids. Submarines are also hybrid vehicles -- some are nuclear-electric and some are diesel-electric. Any vehicle that combines two or more sources of power that can directly or indirectly provide propulsion power is a hybrid. Most hybrid cars on the road right now are gasoline-electric hybrids, although French car maker PSA Peugeot Citroen has two diesel-electric hybrid cars in the works. Since gasoline hybrids are the kind you'll find at your local car dealership, we'll focus on those in this article.

Gasoline Power vs. Electric Power

The gasoline-electric hybrid car is just what it sounds like -- a cross between a gasoline-powered car and an electric car. Let's start with a few diagrams to explain the differences between a gasoline-powered car and a typical electric car.

A gas-powered car has a fuel tank, which supplies gasoline to the engine. The engine then turns a transmission, which turns the wheels.

Gasoline-powered car
Move your mouse over the parts for a 3-D view.

An electric car, on the other hand, has a set of batteries that provides electricity to an electric motor. The motor turns a transmission, and the transmission turns the wheels.

Electric car
Move your mouse over the parts for a 3-D view.

The hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while overcoming the shortcomings of an electric car.

To be useful to you or me, a car must meet certain minimum requirements. The car should be able to

Drive at least 300 miles (482 km) before re-fueling

Be refueled quickly and easily

Keep up with the other traffic on the road

A gasoline car meets these requirements but produces a relatively large amount of pollution and generally gets poor gas mileage. An electric car, however, produces almost no pollution, but it can only go 50 to 100 miles (80 to 161 km) between charges. And the problem has been that the electric car is very slow and inconvenient to recharge.

A gasoline-electric car combines these two setups into one system that leverages both gas power and electric power.