LED Bulbs vs LED Conversion Kits: How to Choose

April 02, 2021 8 min read

Kit vs Bulb

If you've spent any time shopping for LED headlights, you might have seen some people selling LED bulbs, and others selling LED conversion kits. What you might not know is the difference between them. Which is which, and which do you need? 

The answer is likely longer and more nuanced than you might expect. LEDs are simply bulb-shaped devices of semiconductor diodes that emit light when voltage is passed through them. A kit includes a few or several accessories on top of the bulbs, to make replacing it possible or easier.

Bulbs vs Conversion Kits: What's the Difference?

LED bulbs are exactly what they sound like. An LED bulb is a simple bulb made out of LEDs, a housing to contain them and protect them from the elements, a heat diffuser, and a connector that plugs into the same connector a standard bulb does.

Difference Between Them

LED bulbs may or may not have additional technology included in them. For example, some bulbs have microchips that have Bluetooth connectivity, which allows you to control their brightness and color from your smartphone. 

Bulbs are exactly the form factor you might expect; they're the size and shape of any other headlight bulb. There's nothing more to them. Though, it may be worthwhile to remember that LEDs are not bulbs in the traditional sense; they have no filaments and emit light differently than regular bulbs.

Kit Examples

A conversion kit is a kit that contains a bulb, as well as some additional accessories that might be necessary for your vehicle. If your vehicle needs something to allow LED bulbs to work, that accessory will be included with the kit for your vehicle. If your vehicle does not require anything but the bulb as a plug-and-play upgrade, you likely do not need a kit at all.

What's Included in a Conversion Kit?

So, what is included in an LED conversion kit? There can be several different parts, which may or may not be included with every kit. Generally, LED bulb manufacturers will include the items necessary for a specific vehicle in a vehicle-specific kit, so you will need to make sure you purchase the right kit for your vehicle. What might that kit contain?

Whats Included

Additional Heat Diffusers. LEDs are not as hot as halogen or xenon bulbs, but they are very sensitive to heat and have no real way to diffuse it other than passive radiation. Many LEDs are built with a heat sink in mind, but some may have additional heat diffusers included in the kit. These can take up additional space and, depending on your vehicle, may make the bulb more difficult to install.


Fans. Some LEDs opt to use small fans to circulate air and keep the LEDs cool, rather than relying on passive airflow over a heat sink or other passive cooler. These require more power than the LED on their own and may require an additional connection to the wiring harness in your vehicle, though some have the fans built into the LED directly and will not need any special connections.


Current Regulators. Depending on the kit you buy, you may or may not need a current regulator. LEDs draw much less power than halogens and far less than xenon bulbs, and so the voltage reaching them needs to be stepped down. This requires a regulator to prevent the bulbs from burning out. Most modern LEDs have this circuitry built into their design, but some older-style LEDs and some more barebones kits may require a separate current regulator.

LED Regulator

Wiring Adapters or Harness Replacements. In some vehicles, particularly much older vehicles, the wiring harness may not be set up in a way that allows a replacement LED bulb to function. There may be space considerations, wire considerations, or adapter considerations that get in the way. In these cases (which are, thankfully, rare) you may need to replace more of your overall wiring harness to get the replacement LEDs to function properly.

Wiring Harness

Error Cancellers or Decoders.More recent vehicles have sophisticated computers and networks of solenoids and other sensors that detect the proper operation of the vehicle. These computers are responsible for your dashboard warning lights and for other issues, including errors in the computer itself that are visible to mechanics.

Error Canceller

Because LED bulbs don't require the same power draw, and may have additional hardware added to the system, the computer for the vehicle does not understand what's happening, and will throw an error to the logs and on the dashboard. Error decoders or cancellers allow this error to be suppressed, so you aren't constantly bothered by a warning light on your dashboard.

Tools. While many vehicles don't need any special tools to replace a headlight, you may need some if you're working with the wiring. Some vehicles also might require a tool to help loosen or remove the existing light bulb or even access the housing in the first place.

Included Tools

A good LED conversion kit will include the tools necessary to do the job, rather than relying on you to make do with what you have at home, or purchase special tools in addition to the kit. These tools might include wiring tools or small wrenches designed to help minimize accidental damage when removing a stuck headlight, as well as any tools necessary to access the light bulb housing to replace the bulb in the first place.

Instructions. Every good kit includes instructions for using all of the above. Low-end kits might have minimal or no instructions, while high-end kits will have step-by-step instructions on how to replace a bulb. Buying a simple bulb replacement is enough if you already know how to replace one, but if you have to use extra accessories, they may require specific instructions.

Conversion Kit Manual

There are also a handful of things that have to do with replacement headlights, but which are not part of LED kits. These include:

Replacement Housings.Generally, LEDs work best in projector headlights. Reflector headlights, the older style on older vehicles, typically requires either an updated reflector bowl or a swap to projector housings. Most LED kits will not include this housing, so you will need to get a replacement separately. On top of that, many older vehicles that have reflector housings may not have projector housings available, or only available as an aftermarket part.

Differences Between Housings

Ballasts. When upgrading headlights, you may have heard of ballasts and wonder what they are and if you need one. For LED upgrades, the answer is no.


A ballast is an electronic component that is required for an upgrade to the Xenon HID bulbs. Xenon bulbs require a high voltage kick to start them and keep them lit. A standard vehicle wiring harness cannot provide that voltage. A ballast stores a charge and help deliver the jolt necessary to kick the xenon on and turn it into the light. An LED bulb does not need this kick and thus does not need a ballast. 

Do You Need a Kit?

Now that you know what's in a kit, you're probably wondering whether or not you need one. The answer is: it depends. To first determine whether or not you need a full kit, you should answer these questions as relevant to your vehicle.

Headlight Photo

Does your vehicle already come with LED bulbs installed? Many more recent vehicles already have LED lights installed by default, either as an option or as a standard feature of their make and model. There has been significant movement in the direction of LEDs over the last decade, and many auto manufacturers now include LEDs for some or all of the bulbs in and around a vehicle.

LED Lights

If your vehicle already has LEDs, but one of them has burned out or stopped working, all you need is a replacement LED for that socket. You don't need a specialized kit, because all you need to do is swap the bulb. All of the hardware necessary to accommodate an LED is already in place. You may need a small wrench or other tools to remove the existing LED, but replacing it shouldn't require much of anything other than simply removing the old bulb and installing the new one.

Bulb Finder

When you search for your vehicle, are the results kits? Our site offers a search engine for the vast majority of consumer vehicles on the road. Simply choose the year, the make, and the model of your vehicle, and you will be brought to a page that lists out all of the light bulbs on your vehicle. Click on your relevant bulb slot – high beams, low beams, fog lights, door lights, or whatever else you want to replace – and check the options.

Are you seeing primarily replacement bulbs or entire kits? If you're seeing kits, chances are that your upgrade requires more than just swapping from a halogen bulb to an LED. If, on the other hand, you mostly see bulbs, you can assume that you don't need anything more than a replacement bulb to swap in.

Are you replacing headlights or a different kind of light? LED bulbs may require additional accessories if they're replacing your high beams, your low beams, or your fog lights. In particular, these are lights that usually have an error attached to them if the voltage is off, which lights up your dashboard. You may need the error decoder or canceller for these installations.

Different Kind of Light

Other bulb locations, such as brake lights, tail lights, dome lights, door lights, and license plate lights, do not require any additional tools or functionality. You can simply replace them with the correspondingly-sized LEDs, as listed on our site search engine. 

Generally, you will only need a kit if you're replacing headlights of some kind. Other bulbs are simple swaps and don't require other accessories or tools.

Example Kits 2

Is the kit you see truly a kit? Oftentimes, you will see a "headlight upgrade kit" for LEDs, but that "kit" does not actually include anything other than a pair of bulbs and, potentially, instructions. Many "kits" are not truly kits and are only labeled as such because they provide everything you need to replace both of your headlights.

This can be convenient, in case you want assurances that your purchase is getting you everything you need for your upgrade. In other cases, you may find that you need to make multiple orders to get bulbs and that one bulb might not match. A kit solves that problem.

Ford Lighting Kits

Are you replacing Xenon HID bulbs? You may need tools to remove the ballast and error canceller from your wiring harness if you're swapping from an HID to an LED bulb. Often, this is the case for vehicle owners who upgrade to HIDs, only to find that they flicker, or that the brightness, color, or delay is too much. HIDs have a few drawbacks that LEDs do not, so it's reasonable to want to swap to avoid dealing with the hassle. Just be careful of the ballast when removing it; it can be a dangerous source of high voltage.

Do you need accessories beyond just a bulb to make your headlights functional? For example, if your headlights have burned out and you're not sure why - you may need to run through a checklist of other accessories. You might need a new reflector bowl, a new housing, new wiring, or a new adaptor. Alternatively, you might just need a new bulb. The more you need, the more likely it is that a kit will give you what you need in one purchase. However, you're more likely to get extra parts you don't truly need if you buy a kit and only need, say, a replacement bulb.

Non Functional Headlight

So, the answer to whether or not you need to buy a kit is varied. You may need a kit for certain vehicles, particularly old vehicles. You may need a kit if your existing wiring is damaged, or on certain vehicles that have more difficult headlight housings.

On the other hand, you will not need a kit if you're replacing existing LEDs, if you're replacing non-headlight bulbs, or if you already know what you're doing and have the tools to do it on hand.

LED LightStreet
LED LightStreet