Headlight technology is evolving at a swift rate and it is getting difficult to choose between the various options available in the market. Apart from the standard ones, the industry is now has new bulb types like halogens, xenons, HIDs and LEDs. With a range of offerings to the customer, it is important to know how each of these are different and more importantly to understand if they fall within the legal terms and conditions of their use.

Light Emitting Diode (LED) Bulbs

LED or light emitting diodes work on the principle of movement of electrons. They release high intensity lights. An advantage of LED lights is that they light up instantly producing light rays of very high intensity. They are highly efficient and have a longer life compared to other light sources. Considering all these advantages, LEDs are preferably used as daytime running lights and tail lights. With evolving technologies, LEDs have powered into the headlight industry to overcome the problem of low light intensities in standard headlights. Another added benefit of using LEDs is that they can emit light that is similar to daylight. Few manufacturers have high and low beam LEDs while others use just low beam. They are less taxing on your car’s electrical system. If a halogen bulb consumes 5 amps, an LED of the same intensity takes up only 1.5 amps.


A halogen bulb is much like any household electric bulb. While a regular household bulb uses a heated-up filament to emit light, a halogen bulb uses a halogen gas to emit high intensity light. Though the use of halogen bulbs in automobiles is over 50 years old, they are still widely used. They emit a yellow light and can cover approximately 100 meters.

High Intensity Discharge (HID) Bulbs

High intensity discharge (HID) light bulbs sends an electrical discharge between electrodes either through an ionized gas or plasma to create light. In addition to this, either mercury, xenon, metal halide or sodium is used as an additional gas and this gas serves as an easy way to classify the major types of HID lamps. The most common type of HIDs used in automobiles are xenon lamps. They produce a bluish-white light, which is very close to natural light. They are more expensive than LEDs and Halogens. However, these are still widely used because they last long. They require a stable surge of electricity to start and regulate the power during operation. Hence, there is always a small delay before reaching full brightness.

Use of Relays in Headlight Wiring

A commonly asked question is if one should add relays to headlight wirings. The answer is a definite yes. Let us first understand why we need to use relays.

Power is conveyed to the lamps from the batteries through wires. Maximum power is transmitted when there is no power loss. However, in practice, there might be few issues that lead to power loss. The thickness of a wire, connectors used and switch rating are all designed based on the specifications of the OEM’s electrical system. Most of the connectors used in today’s systems are not hermetically sealed. This causes corrosion. As time progresses, this produces heat that can cause decay of contacts leading to fire. Contact resistance is another factor that must be considered. As corrosion accumulates, the resistance builds up causing potential damages to the electrical system.

Using a relay ensures that the high current is moved away from the switch. Relays are hermetically sealed and hence do not cause any corrosion.

Excessive Heat Due To High Power Lamps

High power lamps are primarily used for two reasons: whiter light and extra light on the road. A common perception is that the heat generated increases with the increase in the power of the lamp. Greater light output is obtained by using a higher wattage. Using higher wattage bulbs will cause the wires in the system to burn out. A vehicle is manufactured to certain specifications and can only allow small tolerances.

It is true that high-power headlights generate excessive heat causing failure to the electrical system. This may lead to overheating or wire melting. They also cause problems for vehicles with plastic headlight lenses. Manufacturers have come up with innovative ways to increase the power of the lamps without increasing the amount of heat generated.

55 W V/S 100 W Bulbs for Headlights

As discussed earlier, each vehicle is designed to meet certain specifications and allows modifications till a certain tolerance level. Most Indian vehicles are originally equipped with 55W headlights. Doubling the design load can lead to wiring issues. The bulbs will generate a lot more heat thereby damaging the plastic components. The biggest problem while using a 100 W bulb is aluminizing the reflector which either leads to discolouration or flaking off due to the extra heat. This is commonly observed in high ambient temperature regions.