The short version: because your car will have a higher luminous efficacy. Now for

the long version: First of all, we should state that not all HID (High Intensity

Discharge) headlamps are using Xenon as the weapon of choice. Some use Mercury

vapors, other metal halide, ceramic metal halide and others use Sodium vapor.

Secondly, all automobile applications of HID lamps use Xenon, but not all of them use

this gas for the whole functioning time. Now let's see how they actually work.

Even though a common name for most HID lights is HID Xenon Light, most of them are actually metal

halide lamps that contain Xenon gas, which is only used to allow the lamp to produce

a minimal amount of light immediately after power-up, in order to accelerate the

(much longer) run-up time of the lamp. The distinctive blueish color separates HID

headlamps from the regular lamps with tungsten filaments.
Even though they give a greater amount of light output per amount of electricity

power input, and the luminous efficacy transforms a greater proportion of their

radiation is visible light as opposed to heat, HID H lights are still mostly used in low-beam operations

and very rarely on high-beam lamps, even though the proportion varies by the

geographical area. For example, when comparing international ECE standard (which is

recognized all over the world) with the SAE standard (mandatory only in the United

States) we can see that in the US more glare is permitted and actually required for

the headlamps. In other words, the reason most HID Xenon Kits sell in America might not be the buying power but the

permissive legislation. Because of the energy required to run a HID headlight, the

HID bulbs do not run on low-voltage DC current, so they require a power pack

(ballast) with either an external or internal ignitor, which controls the current

given to the bulb. Considering automobiles use a 12-volt electrical system for their

lamps and the HID 90

lighting requires over 20,000 volts to ignite the bulbs and then 85 volts to keep

them running, the ballast is a necessary part of the system.
Apart from turning it on it also regulates the voltage, and is an integral part

of the HID system. The power-up of the bulbs happens in three phases. First comes the

ignition, when a high voltage pulse is used to produce a spark which ionizes the

Xenon gas, creating a tunnel of current between the Tungsten electrodes. After this

comes the initial phase, when the temperature in the bulb capsule rises rapidly, the

metallic salts vaporize and the resistance between the electrodes fails. The ballast

comes into function and automatically switches to continuous operation, when all

metal salts are in vapor phase, the arc of light has achieved a stable shape and the

luminous efficacy has attained its nominal value. Being supplied with stable

electrical power by the ballast, the arc will not flicker. The main advantage of

HID D headlamps is the

increased safety provided by the more usable light compared to regular Halogen ones.
Other hard points are the luminous efficacy, the reduced power consumption and

the longevity (the average service life of a HID lamp is approximately 2000 hours,

while a Halogen lamp has between 450 and 1000 hours of functioning). The

disadvantages on the other hand are also more than enough, especially in the US,

because of the permissive legislation. For example, vehicles equipped with HID

headlamps are required by international ECE regulation to be equipped with lens

cleaning systems and automatic beam leveling control in order to reduce the high

levels of glare induced to other road participants. In the United States, SAE

legislation acknowledges and permits this rule but does not enforce it.
Another downside comes from the lack of backward-compatibility between HID lights

and Tungsten-Halogen headlamps, hence special optics are used to collect and

distribute the light on HID lamps. The cost of producing, purchasing, installing and

repairing HID headlamps is also significantly higher compared to Halogen lamps.
Reliable off-road vision is a cornerstone of vehicular safety – it goes without

saying that being able to see where you’re going makes a world of difference. Modern

LED technologies have made this safety accessible to everyone.
LED Conversion Kits

have plug-and-play installation and produce between 4000 – 8000 lumens while using

less wattage than stock halogen bulbs. They also last up to 10x longer than

incandescent bulbs, with a massive difference in brightness.