Advice

Car Headlights: A Complete Guide

By 01/15/2025 3:00pm
2023 Mazda CX-50 headlight on.

Quick Facts About Car Headlights

  • Headlights lose a degree of brightness with each use.
  • LED headlights are brighter, last longer, and burn less energy than halogen or HID headlights.
  • Other factors, like a loose wire or failing battery, rather than worn-out bulbs, can cause headlights to dim.

If you are pondering car headlights, the odds are that you are either on a quest to replace your current vehicle’s headlights or car shopping and attempting to understand the many headlight technologies available on today’s cars. In either case, the question is, why does one headlight type work better than another, and which is better?

The innovative design and functionality of headlights have become so popular over the decades that we now have several solid headlight choices from which to pick. These lights and systems include some you can buy for your existing vehicle and others you can only acquire with a new car or truck. Our headlight guide can help unravel some of the mystery and, well, cast some light on headlights. Use the jump links below if you want to skip ahead.

What Are the Key Technologies of Modern Headlights?

As does technology in general, headlight technology continues to evolve. Engineers and designers specializing in headlight development have four key goals in mind as they push headlight technology forward:

  • Smaller
  • Brighter
  • More efficient
  • Longer-lasting

In other words, the idea is to make a brighter headlight that consumes less energy and lasts longer but occupies a smaller area on your car’s face.

Headlight Features to Be Aware of When Upgrading

 Every journey begins with a first step. When upgrading headlights, the first step is understanding several headlight factors that you should consider.

  •  Compatibility: Not every headlight can fit your specific vehicle. Consequently, your first stop should be your new vehicle owner’s manual. If that doesn’t answer your compatibility questions, check with the parts desk at a franchised dealer.
  • Color Temperature: Light is light, right? Nope. A headlight’s color varies according to the temperature at which it burns. The lowest temperature produces yellow. As the temperature increases, the color moves to white, blue, and even a shade of purple. Yellow is best for fog and snow. The hotter the temperature, the more effective the headlight is for clear-weather nighttime duty.
  • Brightness: Particularly with older bulb technologies, the brighter the light, the shorter the bulb life. This conventional wisdom doesn’t hold true with LEDs, but it does with most other types of bulbs.
  • Quality: With so many headlight manufacturers worldwide, buyers must beware. We recommend doing a little product research before you buy because every replacement headlight isn’t created equal. 

When Do You Need to Replace Headlights?

Industry experts say the average life expectancy of car headlights is about five years. More modern headlights like LEDs will last longer.

Here’s what you may not want to hear: Your headlights are wearing out each time you engage them. Headlights grow dimmer over time — every day. However, like someone growing older whom you see daily, the day-to-day change in your headlights’ brightness is so subtle that you don’t notice. 

Most of us don’t worry about replacing a headlight until it stops working. However, a good rule of thumb is to get yours tested if you haven’t replaced them in the past five years. You can do it yourself with a digital light meter or take your vehicle to a professional. 

 3 Signs You Need New Headlights 

  • Your vehicle’s headlights grow noticeably dimmer.
  • The headlights begin fluctuating in brightness.
  • One of your headlights burns out.

How Often Should Headlights Be Replaced?

The majority of cars on the road use halogen headlights with a life expectancy of 500 to 1,000 hours. Even if your headlights don’t appear to be dimming, you should check them out after five years and then every year after that. 

What Are the Types of Headlights? 

There are multiple types of headlights and headlight bulbs on the market today. What’s available can vary by car manufacturer and even by a manufacturer’s models. Here are the most popular types of headlights.

Reflector and Projector Headlights

Reflector headlights are old-school, while projector headlights are a newer take on reflector technology. 

A reflector headlight was originally a single component consisting of a bulb encased in a reflective steel bowl covered by a glass (or plastic) lens. The bowl served to spread the bulb’s light over a wider area as the glass lens directed the bulb’s light in a specific pattern. 

Eventually, mirrors inside the housing reflected the bulb’s light, directing its beams. This effect freed the housing from the lens. In other words, you could now replace just the bulb rather than the entire component. Reflector headlights remain popular with carmakers because of their low cost and compact size. 

Think of projector headlights as a more refined version of reflector headlights. 

The primary ingredients remain a bowl, mirrors, and bulb, but a magnifying lens increases brightness. Because of the added shine, the housing also includes a cutoff shield, directing the light beam downward to prevent blinding approaching drivers. 

This technology costs more than a regular reflector headlight, but projector headlights provide a brighter, more even light and don’t shine in the eyes of other drivers. Moreover, projector headlights can accommodate xenon high-intensity discharge (HID) bulbs, as well as light-emitting diode (LED) lights. 

Halogen Headlights

The elder statesman of today’s headlights, halogen headlights, are similar to incandescent lights because they use a filament and gas inside a sealed reflector casing. An electric current passes through the filament, creating light. Today, that light likely passes through a projector lens. 

Still widely used in new cars (nearly 80%), halogen headlights are relatively inexpensive and quickly replaced by do-it-yourselfers. However, they require a lot of energy to function and aren’t particularly bright.

Halogen bulbs are the go-to when low and high beams use separate bulbs. A halogen bulb provides illumination for the high beam, while an HID bulb supplies the low beam. 

HIDs (High-Intensity Discharge) 

The terms “HID” and “xenon” are sometimes used interchangeably, but xenon is really a subcategory of HID. 

As you might have guessed from the “high-intensity” in the name, these are very bright bulbs. A gas mixture surrounds two electrodes enclosed in the bulb. Switching on the electrodes energizes the gas, which produces light. Xenon is one of the gases. 

Not only is HID output roughly two to three times brighter than halogen, but the light color is much less yellow. The HID light color is often so white that it’s bluish. 

HID has several advantages over halogen, including requiring less energy, providing brighter illumination, lasting longer, and looking better.

Xenon 

Xenon bulbs are a bit more complicated than HID. However, they use the same basic arc-across-two-electrodes technology. With xenon, though, the gas surrounding the electrode is nearly all xenon. 

Bi-xenon 

Bi-xenon refers to a double-beam system in which both are HID bulbs. Its technology is more involved than that, which also adds to the cost, but essentially, HID bulbs function as high and low beams. 

Because it produces a brighter light than a halogen headlight, bi-xenon uses roughly 60% less power and lasts at least twice as long as halogen. 

LED (Light-Emitting Diode)

Although LED headlights (taillights, daytime running lights, and fog lights) are one of the biggest, hottest things on new cars, LED isn’t new to vehicles. Many of the little warning lights on your instrument panel are probably LEDs. However, using LEDs for exterior lighting is a relatively new development. 

In a nutshell, an LED is a light-emitting diode. A diode is nothing more than a semiconductor that allows current to flow through it in only one direction. A light-emitting diode is designed to emit photons as the electrons pass through it. It’s the photons producing the light we see. Bundled diodes work as a cluster in the case of LED headlights. 

Although LEDs are expensive to replace, they outlast halogen and HIDs by years. They also require less energy and generate less heat. 

LED Matrix 

Here’s where the coolness factor kicks in. In relation to LEDs, a matrix is simply the environment in which the LEDs reside. You can program the matrix so that the LEDs divide into sections. The LEDs can burn lower intensity in one section, while they can burn higher in another. Consequently, the low and high beams live on the same matrix encased in the same housing. 

When connected to a forward-pointing camera, the matrix can turn off or lower the intensity of one or more sections when the system detects an approaching car. The shift happens in the blink of an eye. 

There’s your automatic high-beam assist. With this setup, if your headlights are on, the high beams are on. Only when the system detects approaching headlights does it dim or extinguish the high beams.

The advantage presented by matrix LED headlights is that they provide high-beam coverage without driver input. Of course, the other LED benefits are present, as well. 

Halo Rings 

You may have heard or read the term “halo rings.” They are accent lights surrounding the main headlights. With today’s technology, halo rings take three forms: LED, CCFL, and plasma.

  • LED: More often than not, these are plastic tubes surrounding the headlight. If you look closely, you can see the many individual LEDs comprising the ring. Also, because they are LEDs, they burn bright. LED halo rings are available in a variety of colors. You can even buy a module allowing you to change the colors. 
  • Cold Cathode Fluorescent Light (CCFL): CCFLs are a more traditional approach to halo rings. In essence, a CCFL is a glass tube filled with glowing gas. The effect is a smooth, consistent appearance rather than all the pinpoints of light created by LEDs. That’s the CCFL’s advantage. However, there are three major disadvantages. First, LEDs burn brighter. Second, you can’t program CCFLs for different colors as you can with LEDs. Third, CCFLs don’t last as long as LEDs. 
  • Plasma: Plasma is a more sophisticated approach to LED halo rings. Each LED makes contact with the circuit board, which turns the entire halo into one solid LED. Plasma isn’t as bright as LED, but it provides a solid appearance rather than dots of light. 

What Are Lumens?

A lumen is a standard measure of brightness. A single lumen roughly equals the light of one candle. The higher the lumen rating, the brighter the light. 

What does that mean for headlights? Here’s a breakdown of the average lumens put out by headlights by type, according to NADAguides: 

  • Halogen bulbs: 700 lumens
  • HID/xenon bulbs: 3,000 lumens
  • LED bulbs: 2,000-4,000 lumens

What Are Adaptive Headlights? 

Also called “active headlights,” they are still mostly found as an option on higher-end cars and trucks. 

They swivel, following the direction of the steering wheel input. If you make a right turn or turn into a right corner, the headlights swivel to the right. Make a left turn, and the headlights swivel left. The goal is to illuminate the area into which you are turning. 

According to the Insurance Institute for Highway Safety (IIHS), some early studies have shown that nighttime collision and property damage claims fell by 10% to 15% for cars equipped with adaptive headlights. 

What Are Auto-Leveling Headlights? 

Auto-leveling (or self-leveling) headlights are primarily a feature found on trucks and SUVs, but they are trickling down into other vehicles, too. Many cars with adaptive headlights boast a self-leveling feature, too. The idea is to keep the headlights at a constant level. When level sensors determine the front end is rising or dipping, electric servomotors in the headlights compensate by rolling the headlights up or down. 

In trucks and SUVs, an extra-heavy load of cargo or towing can force the front end upward. Consequently, the headlights rise and can blind oncoming drivers. Auto-leveling headlights minimize the effect of a heavy load. 

What Is Headlight Alignment? 

Unless your headlights use some sort of self-leveling scheme, they may go out of alignment. This misalignment can happen through wear and tear, a fender bender, or as a result of replacing a headlight. 

If you feel as though your headlights don’t illuminate a long enough or wide enough path, they may be out of alignment. Another sign is that if drivers are flashing their high beams at you when your high beams aren’t engaged, then at least one of your headlights is too high. 

How to Check Your Headlight Alignment 

  • Pull your vehicle within five feet of a wall or garage door.
  • Make a cross at the center of each headlight beam using masking or painter’s tape.
  • Back up the vehicle 20 to 25 feet. If either cross strays from the center of the beam, your headlights need alignment.
  • Having your headlights professionally aligned will set you back roughly $50 on average.

What Are DOT- and SAE-Approved Headlights?

When shopping for headlights, you will run across a couple of different labels. One is DOT, which stands for the Department of Transportation. Finding that seal means the headlight is legal for use in the United States. 

The second label is SAE. It represents the Society of Automotive Engineers, an organization monitoring standards for parts and personnel in the automotive industry. Its seal has nothing to do with legalities but does mean the part with the seal fulfills whatever standards SAE has established for that part. 

Why Are My Headlights Dim?

Headlights can dim for several reasons, not the least of which is the headlight is wearing out. 

What Is the Average Life of a Headlight? 

Light Type Approximate Hours of Life
Halogen 500-1,000  
HID 2,000-3,000  
Xenon 10,000
LED 30,000

Other Reasons for Dim Headlights

Although the odds are good, dim headlights mean worn-out headlights, but that’s not always the case. 

  • A bad ground wire – A common issue in older cars is a faulty ground wire running from the headlight terminal to the vehicle’s chassis. 
  • A failing battery – This is the case if the lights are dim when the ignition is off but brighten when you engage the ignition. 
  • A loose alternator belt – Everything else could be fine, but a loose alternator belt can reduce the juice to electric components, causing the lights to dim. 
  • A failing alternator – Because it powers all the electronics in your vehicle, a bad alternator will starve your electronics of power, beginning with the headlights. 

How to Clean Car Headlights

Chronically dirty headlights may not come clean with soap and water. If that’s the case with your car or truck, try this trick. 

  1. After washing the headlights with soap and water, let them dry completely. 
  2. While waiting, use painter’s tape to mask off the painted and chrome areas around the headlights. 
  3. Squirt some toothpaste on a soft cloth. Using a firm circular motion, apply the toothpaste to the headlight lens. Spend a few minutes on each lens. 
  4. Rinse with water and allow to dry. 
  5. Buff off the haze with a soft, clean cloth. 

How Do You Remove Moisture From Inside Car Headlights?

Heating the glass or plastic lens with an electric hairdryer is the most effective way to remove trapped moisture without breaking the seal. Applying heat causes the moisture to evaporate.