Automotive lighting systems differ from car to car and can easily get confusing for those not very familiar with cars in general or car lighting more specifically.
Whether you're looking to replace halogen bulbs or to upgrade LED or HID headlight bulbs using an aftermarket conversion kit, understanding your car's lighting system is critical to purchasing the right bulbs.
All cars and trucks come with a low beam and a high beam function, however, some cars require two separate bulbs (single beam systems) while others require only one bulb (dual beam systems).
After reading this guide, you'll understand the differences between a single beam and dual beam headlights system and the difference between low and high beams. We'll also explain when you should use your low beams and high beams and conclude with some questions we frequently receive from our customers.
Most of the confusion surrounding headlights is the difference between single beam bulbs and dual beam bulbs. Briefly speaking, a single beam headlight system uses two headlight bulbs, one for the low beam and another for the high beam. On the other hand, a dual beam headlight system uses one bulb for both the low and high beam.
|Single Beam||Dual Beam|
|Number of bulbs||Two (2)||One (1)|
|Number of filaments||One (1)||Two (2)|
|Low beam function||Yes||Yes|
|High beam function||Yes||Yes|
|Price of bulb ($)||Lower||Higher|
|Examples||H7, H11, 9005, 9006||H4, H13, 9004, 9007|
|Impacts fog lights||No||No|
The name 'single beam' often confuses drivers, leading them to believe the headlight requires a single bulb, however, it's quite the opposite. Dual beam systems require only one bulb for both beams as we explain in the next section.
Single beam headlight bulbs such as H11 and 9005 work exclusively with one beam, either the low or the high beams. As such, single beam systems require two bulbs total, one to create a light beam for the lows and a second to create a beam for the highs. Single beam bulbs have one filament, which means it only emits one beam of light at a time.
Dual beam headlight systems work with one specialized bulb that can create two beams (low and high beams). Dual beam bulbs such as H4, H13, 9004 and 9007 have two filaments, which allows them to create two beams (high and low) when both are activated.
The name 'dual beam' is misleading as drivers often think it means the headlight system requires two bulbs but as explained, dual beam systems require one bulb for both beams.
The difference between low and high beams is that low beams are used for normal nighttime driving while high beams are used in rural areas or small roads with very little or no light at all. Low beams are angled towards the road and should be always kept on in low light settings while high beams are angled upwards for extra light and should only be used for very short periods of time as to not blind other drivers.
As mentioned earlier in this guide, all cars have a low and high beam function, regardless of whether the headlight uses single or dual beam bulbs. Most drivers should already know the difference between the two since it's a prerequisite before getting your license. Also, this topic is a lot less confusing than single beam versus dual beams bulbs.
|High Beam||Low Beam|
|Beam Angle||Straight/Upwards||Towards the ground/road|
|Light Coverage||~100 meters||~40 meters|
|Best For||No light environments (rural areas, small roads, etc.)||Nighttime driving / low light environments|
|Activation Period||Short period / as long as no other cars are within 150 meters||Must always stay on when in low or no light environment|
|Blind other drivers||Yes||No|
|Activation||Manual||Automatic or Manual|
Low beams are the 'normal' lights your car headlights emit and are used when driving at night or in a dim or dark setting such an indoor parking lot.
Low beams are the most important and most frequently beam used in a car. The light beam is angled towards the ground in order to illuminate the road and to avoid blinding other drivers.
Traditionally, drivers would have to manually turn on their low beams but newer cars do so automatically by detecting low light environments.
The light beam for high beams is angled upwards in order to illuminate a surface area above and beyond the light or the low beams. The high beam headlight lighting function is normally activated in environments with little to no light such as the country or small roads with no street lights.
Unlike low beams, high beams will never turn on automatically. They must be manually turned on by the driver when needed. In fact, high beams should only be used for short periods of time when extra light is really needed.
Driving with your high beams can blind oncoming traffic, which can be very dangerous. Keeping them on for an extended period of time is illegal.
No. Using a dual beam bulb for a single beam system will not work. A dual beam bulb will not fit and comes with 2 filaments, something your single beam headlight system is not equipped to handle. You will need two sets of the specific bulbs for your car for each of your high and low beams.
No. Using a single beam bulb for a dual beam system will not work. A single beam bulb will not fit and only has one filament, which means that your high beams would not work even if the bulb did fit. You will need one set of the specific dual beam bulbs for your car's dual beam system.
This entirely depends on your car. Some cars happen to use the same bulb size for each of the high and low beams in a single beam system while others use completely different bulb sizes. In the event that they are the same, you will need to sets of bulbs, one set for your lows and another for your high beams.
Yes. Whether your car requires a single or dual beam bulb depends on your vehicle's headlight system, not the bulb technology.
So, if your car comes equipped with dual beam bulbs, you will need to get the exact same bulb size when upgrading your lights to either LED or HID.
9005 is a single beam headlight bulb. This is one of the most popular bulb sizes.
H13 is a dual beam headlight bulb, it is one of the most popular dual beam headlight bulb sizes.
Generally, the bulb is the one that is dual beam since it's the part of the headlight system that has the function to emit two light beams. It can be argued that the headlight is also a dual beam since it only has room for one dual beam bulb.
However, for a very limited number of cars, it is the headlights that are dual beam. These headlights come with a flap function that creates two beams out of one bulb.
Fog lights always use single beam bulbs since they can only emit one light beam unlike headlights, which must emit both a high and low beam regardless of whether a single or dual beam.
Bi-xenon bulbs are dual beam bulbs where both filaments (beams) use HID/Xenon technology. This specific term exists because HID/Xenon dual beam bulbs can come in a second form, where the low beam is HID/Xenon technology and the high beam is halogen, in which case it is called a hi/low bulb.
Many people often think bi-xenon simply mean dual beam but that is not accurate. For example, asking for a bi-xenon LED bulb technically makes no sense at all.
Look at your car's headlight to see whether there are one or two bulbs. If you see two bulbs, you have a single beam system. If you only see one bulb, you have a dual beam system. Do not count the turn signal bulb should your car's headlight come with one.
Alternatively, you can use our Vehicle Finder tool. Should your car have a dual beam system, you will see one the following dual beam bulbs listed: H4 (Dual-Beam), H13 (Dual-Beam), HB2 (Dual-Beam), 9003 (Dual-Beam), 9004 (Dual-Beam), 9007 (Dual-Beam), 9008 (Dual-Beam), D1S (Dual-Beam), D2S (Dual-Beam), D2R (Dual-Beam).
No. High and low beams use bulbs with the same intensity and brightness. Due to their upward angle, high beams cover more territory and therefore appear to be brighter.