Often tauted as the Green machine, Hybrids have led the way to reduced emissions and improved gas mileage. The typical Hybrid is a combination of engine and electric motor. The additional horsepower from the electric motor assist, enables the use of smaller engines, further reducing emissions and improving gas mileage.

It is typically believed that Hybrids, like the all-electric vehicles (EVs) of the recent past, would require to be plugged-in to recharge the batteries. However, the on-board batteries of the Hybrids are recharged by capturing the kinetic energy produced when the car is coasting or braking (called regenerative braking), or by the engine directly.

Hybrids fall into two groups: Full and Mild. Full Hybrids describe a system is which both the engine and electric motors drive the vehicle. Either can work together or separately. The engine is turned off to conserve fuel when the vehicle is at a standstill, or when coasting. The electric motor, without the engine, drives the vehicle during slow acceleration or when the vehicle requires only a small amount of power. This type of Hybrid is available from Ford, Toyota, and Lexis.

Mild Hybrids use the electric motor primarily to supplement the gasoline engine under heavy demand. The electric motor is smaller, and never drives the vehicle by itself. It also shuts off the engine when at a standstill. This type of Hybrid is used by General Motors and Honda.

Still struggling with Full vs. Mild? The next set of terms, Parallel vs. Series, is guaranteed to add to the confusion. I will try my best to keep it simple.

In a parallel Hybrid, the fuel tank supplies power to the gasoline engine while at the same time the battery provides the power to the electric motors. Both the engine and motors can be used to drive the vehicle together.

In a series Hybrid, the engine charges the batteries and the electric motors drive the vehicle. The engine never directly drives the vehicle.

Today's Hybrids are predominantly parallel Hybrids. By 2010, auto manufacturers will be introducing the more radical design of the the series Hybrid. These new Hybrids will also be pluggable.

While the pluggable Hybrid does not need to be plugged in (this is optional), the ability to do so will enable the batteries to be recharged while the vehicle is not in use. This will greatly extend the Hybrid's range; a limitation in the past with all electric vehicles.

A dramatic change from the Hybrids above that rely on engine-motor solutions, the Hydrogen Hybrid relies on Hydrogen gas to significantly improve the efficiency of the engine. The Hydrogen Hybrid system is often called an on-demand Hydrogen generator. The Hydrogen gas is used to supplement the fuel in the tank, an approach employed by fleet vehicles for decades to reduce fuel consumption. The engine provides the power for generating the Hydrogen gas through the electrolysis of Water.

The Hydrogen gas (more correctly called oxyhydrogen or HHO) is mixed with the gasoline in the engine cylinder to produce additional power thus increasing the efficiency of the engine. The advantage of this Hybrid is that it is easily adapted to existing vehicles and uses plain tap water for its energy source.