What are HID Headlights?

Headlight bulbs in automobiles have gone through evolutions since the introduction of the car, late in the 19th century. For many years, halogen bulbs were the state of the art, introduced in Europe during the 1960s and then gaining widespread use right up to the present day because of their low cost.

In the 1990s, some luxury automakers began introducing high intensity discharge, or HID, bulbs in their vehicles. The HID bulbs were able to produce light at much higher levels of intensity while requiring smaller housings and became the choice of lighting options in the luxury car market. The higher light output was sold as a safety feature, while the reduced housing size allowed carmakers more flexibility in designing the front fascia of their vehicles.

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How HID headlights work

The simple version is that HID headlight bulbs create light by arcing electricity through Xenon gas, between two electrodes. If you’ve ever seen a neon sign in a local shop, you’ve seen the same process at work, with an electrical current arcing through a noble gas, in that case being neon.

An HID headlight uses the same fundamental principles as those neon store lights, but with the intent of projecting the light forwards, rather than lighting up an “Open” sign.

The process starts with the ballast, which is an electronic device that can alter the voltage being sent to the bulbs. Your car uses a 12-volt electrical system, but an HID bulb requires higher voltage to start the arcing process, so the ballast increases the voltage temporarily to get the bulbs started and then regulates the voltage going forward.

The electricity flows to the first electrode and the electrode causes the current to spark across to the second electrode. These electrodes are housed within a quartz chamber that is filled with xenon gas. The electricity coursing through the xenon gas excites the molecules in the gas, causing it to produce light, which is projected forward by the bulb.

HID bulbs differ from halogen bulbs in that the electrical arc travels through gas instead of moving through a tungsten filament. Some of the xenon in an HID bulb gets destroyed in the process of producing light in this way, so HID bulbs do have an expiration date, but you will typically notice a gradual reduction in light production as your HID bulbs begin to fail, as opposed to the abrupt failure you will often experience with a halogen bulb.

What are the benefits of HID headlights?

HID headlights are much more efficient than halogen bulbs, producing more light with less power, reducing the strain on your vehicle’s electrical system, and improving fuel economy over the long run. A typical halogen bulb will convert about 20% of its energy into light, with the other 80% becoming waste heat. HID headlights are almost the inverse of that, converting more than 70% of their energy into light, and wasting less than 30% to heat.

Another advantage seen in HID headlights is their ability to produce high amounts of light when compared to halogen bulbs. The frequency of an HID bulb will also tend to be whiter than a halogen, producing light that is comparable to daylight, rather than the yellowing coloration of most halogens.

HID headlight bulbs are more expensive than halogen bulbs but are almost always less expensive than their LED counterparts.

The final advantage of HID headlights is style. Halogen bulbs require large reflective housings, but HID lights can be made much smaller, allowing auto designers and aftermarket customizers the chance to create interesting shapes to enhance the look of your vehicle.

Delta Light 5-3/4in Classic Hi/Lo Beam Hid Headlight Et With Halo 1 Pair
Delta Light 5-3/4in Classic Hi/Lo Beam Hid Headlight Et With Halo 1 Pair

How do I know if I have HID headlights?

Your first source of information should always be your vehicle owner’s manual. It will have specifications for all the wear items, including headlight bulbs, that your car will require over the course of its service life.

Another good source of information is a reputable auto parts supplier like AutoZone where you can search for parts using the year, make, model, and engine size of your vehicle to determine the perfect original equipment fit for any replacement parts. Light bulb sizes and types appropriate for your car are listed conveniently for you to choose from.

A quick call to the dealer or your local mechanic can also yield good information, if you still aren’t certain.

Can I replace HID headlights with another type of light?

Most HID headlights are used in a projector-style headlight configuration because this setup is favorably suited to the design of an HID bulb. Typically, halogen or LED bulbs are used in a reflector-style application, so if your vehicle came with HID headlights, you should probably replace any failing bulbs with an HID headlight bulb replacement. Check the owner’s manual for that information. HID bulbs also produce more light than halogen bulbs, so replacing your HID bulbs with halogens would reduce your nighttime visibility.

Can I replace halogen with HID?

There are several aftermarket suppliers that provide kits to replace your halogen headlight bulbs with a set of high intensity discharge bulbs. The range of prices for replacement kits range from less than $50 to several hundred dollars and it’s important to ensure that you purchase high-quality parts for this type of upgrade, to avoid damaging your vehicle electrical system. You can purchase just the bulbs, or for some vehicles you can get full headlight housings to change the appearance of your vehicle and improve nighttime visibility. A new HID headlight housing can dramatically update the appearance of an older car and give you that special touch to make your ride stick out in a crowd of cars.

Can HID lights damage your car?

Poorly installed or low-quality parts can do damage to your vehicle’s electrical system due to the difference in wattage and voltage required for HID lights but a properly installed, high-quality aftermarket HID conversion kit should not damage your car. Invest in proper parts and you should enjoy your new HID light for many years to come.

Whether you’re searching for car accessories to dress up your car or replacement bulbs for any make and model, AutoZone is your source. If you’re uncertain about fitment, ask an associate for Trustworthy Advice, and shop online for fast delivery options.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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