Fitting HID lights, with their distinctive bluish tint, have become quite a popular part of car customization in recent years. Not only do they enhance the aesthetic appeal of your car, but they are also last longer and are more power efficient than ordinary halogen light bulbs although they are more expensive. And they are brighter which means they contribute to car safety during night riding as well.
HID lights differ from the ordinary halogen lights as they don't have a filament, instead an electric arc between two electrodes are used to create light. They are also called xenon lights because they use xenon gas to produce adequate light immediately upon being switched on. The first xenon headlamps were introduced to the European market by BMW in 1991 as an optional extra on the BMW 7-series. Today's HID lights have evolved to a standard operation, making them cost effective and easy to install as an aftermarket product. The standard operation consists of a high voltage pulse that produces the initial spark when the lights are switched on. However, the car's battery only produces low voltage current; therefore a ballast that ignites the light and then regulating the power flow is required to produce the initial high voltage on start up and then a constant voltage during continuous operation.
Unfortunately, the arc light source in an HID headlamp is not compatible with the filament light source used in tungsten-halogen headlights as they are different in size, shape, orientation, and luminosity distribution. Thus, installing HID lights is not just a matter of replacing the filaments and installing the ballast. Instead, complete HID headlights, with HID-specific optics are required. It basically means you need to replace the whole headlight and not just the little bulb that houses the filament.