High-intensity discharge headlights use an electrical charge to ignite xenon gas in a capsule rather than the tungsten filament used in a standard headlight. A ballast regulates the voltage used to ignite the gas.
The light produced by an HID headlight is close to natural daylight in color temperature and is brighter than a halogen bulb while using less energy. The bulbs take 15 to 20 seconds to reach full light output, and the arc tube must cool for five to 10 seconds before relighting. HID headlights have a longer lifespan than standard headlights because they do not have a filament to burn out.