Under the skin: Why LEDs are a bright idea for fuel economy

It’s an often overlooked fact that the headlights you turn on at night to read the road ahead are directly linked to what comes out of the tailpipe or the range of an EV. Why? If all the lighting on a car, including indicators, is by LED, the power consumption saving compared with using old-school halogen is 60%, and cutting that reduces fuel consumption and emissions. 

The colour temperature (measured in kelvin and literally the colour of the light) is much whiter than a halogen bulb, which is yellow by comparison, giving superior forward vision. Audi quotes 5500 kelvin for its LED headlights, which, it says, is close to daylight. 

LEDs – light-emitting diodes – are classified as semi-conductors, so named because they are more conductive than something like glass but less than a metal, like copper. Diodes were originally developed as electronic components for electronic circuitry and act like a valve, allowing current to flow in one direction but not the other. If certain materials are added to the semi-conductor in a process called ‘doping’, the material can glow (fluoresce) when the diode is live, giving rise to the LED we all know and love. The type of LED used in headlights emits a mixture of red, green and blue light, which the eye sees as white. 

Apart from the free lunch scenario – lots of light for not much energy – LEDs have other benefits, too, such as the potential to shape the beam to light only specific areas of the road. This trickery, known as LED matrix lighting, is made possible by using an array of LEDs in a headlight arranged in separate ‘pockets’ or ‘tunnels.’ Selective use of the LEDs can alter the shape of the beam so that the light pattern can be cut off vertically and horizontally. For example, instead of a traditional dip beam, the road in front of the car on the nearside can remain illuminated further ahead, while that on the offside can be left in relative darkness to avoid blinding oncoming cars.