What Are HID Headlights?

Updated: Jan. 24, 2024

High-intensity discharge (HID) automotive headlights produce a brighter, directed beam than traditional headlights, making nighttime driving safer.

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Your vehicle’s headlights are an essential safety feature that shouldn’t be ignored. According to the Insurance Institute for Highway Safety (IIHS), “Driving at night is three times as risky as driving during the day.”

From the 1920s to the 1970s, cars came with the same nondescript incandescent (sealed beams) headlights. Brighter and replaceable halogen headlights were introduced in the 1970s, and even brighter high-intensity discharge (HID) headlights became available as an option in the 1990s.

HID headlights improve driving safety by illuminating more of the road in front of us without blinding oncoming traffic.

What Are HID Headlights?

HID headlights “discharge” a powerful light beam by igniting high-pressure xenon gas.

Unlike traditional vacuum-sealed or halogen headlights with filaments, HID headlights generate an arc between two tungsten electrodes, turning the gas into blazing-hot, vivid white light.

Housed in thermal-resistant quartz glass, HID headlights can be up to five times brighter than yellowish-tint halogen bulbs. Because the bulbs are so bright, proper headlight adjustment is critical.

Types of HID Headlights

There are two types:

Standard (or single) HID headlights

These are used for vehicles with four headlights: two low beams and two high beams.

Dual-beam HID headlights

More common are dual HID headlights, a single bulb for low and high beams. Single and dual-beam HID headlights are not interchangeable.

How To Choose HID Headlights

Kevlin Scale GraphicFAMILY HANDYMAN

Which HID you need depends on whether your vehicle came with HID headlights, or if you’re upgrading from halogen to HID.

Most headlamp assemblies, i.e. the housing or capsule where the bulbs are mounted, are marked D1S for HIDs or HAL for halogen. HID headlights cost more, but last longer and are more energy efficient than halogens.

If updating or replacing burned out HID headlights:

  • Always replace in pairs.
  • HID headlights, like bulbs used in our homes, come in various color temperatures or tints, rated in Kelvins (K). These range from a warm yellowish (3,000K) to an eye-piercing, ice-cold bluish purple (12,000K).
  • HID headlights producing 4,300K to 6,500K (equal to sunlight at noon) offer the best visibility
  • Matthew Brumbelow, senior research engineer at IIHS, recommends headlights that meet the Code of Federal Regulations, making them legal in all 50 states.

Depending on your driving habits, you may want to consider upgrading from halogen to brighter, whiter HID headlights that better illuminate the road. HIDs are especially helpful at night, especially at highway speeds or on poorly lit country or back roads.

Aftermarket HID headlight kits are relatively inexpensive, easy to install, and come with everything you’ll need.

Do your research. Unlike halogen headlamp assemblies, HID assemblies employ a shield that focuses the powerful beam away from oncoming traffic and onto the road. Halogen assemblies do not have or need this feature. If your halogen assemblies are not compatible, consider aftermarket assemblies “tuned” for HID bulbs.

How To Install Replacement HID Headlights

A straight-up HID to HID bulb replacement is an easy DIY undertaking. Because HID bulbs house high pressure gas, always wear eye protection and work gloves.

Some headlamp assemblies may need to be removed to replace the bulb. This usually involves loosening, at most, two or three plastic thumbscrews or fasteners. Before you begin, check your owner’s manual or an on-line service manual so you can gather the proper tools. At most, you’ll only need a socket set with extensions, a screwdriver set and needle-nose pliers.

Follow these steps to replace a HID headlight bulb:

  • Park on level ground and disconnect the battery.
  • Because you’re replacing both bulbs, wait 10 minutes for working headlights to cool.
  • Unplug the wiring harness from the headlight.
  • Release the retaining clip holding the HID bulb in place and remove the bulb.
  • Carefully clean the new bulbs with a clean, dry microfiber cloth.
  • Be careful not to touch the glass housing while installing.
  • Reverse the steps, checking the retaining clips are securely holding the bulb in place.
  • Reconnect the battery, then check bulb operation and headlight alignment.

Installing an HID Conversion

  • Check headlight alignment first to ensure sure they’re aimed in the same direction as the bulbs you replaced.
  • Follow the same steps as above for replacing an HID headlight per the manufacturer’s instructions. Connect the HID conversion kit’s wire harness to the vehicle’s factory headlight harness, then to the bulb.
  • Recheck headlight alignment and bulb operation.

You should see a remarkable difference between your old halogen and new HID headlights.