Why is Audi pursuing this technology? Simple: LEDs make more light than heat and take up less space. There is another benefit, too: LEDs can be arranged into whatever shapes designers and engineers demand—especially important to a style-leading brand such as Audi.
The common incandescent halogen bulb shines by electrifying and superheating a tungsten filament sealed in halogen gas. Less than five percent of the power consumed results in light, the rest is heat that is wasted. The ratio is somewhat better with high-intensity-discharge, or HID, headlights, where instead of passing over a solid filament, the current arcs between two filaments through a cloud of light-amplifying xenon gas.
Source: Car and Driver