How Are Cigarette Lighters and Accessory Sockets Different?

Does the difference really matter?

There was a time, not so long ago, when a barrel-shaped socket located anywhere in the vicinity of a car's dashboard was invariably a cigarette lighter. Sure, you could use that cigarette lighter socket to power your electronics, but that didn't change what it was. Then dedicated accessory sockets showed up on the scene, and all of that went out the window. These 12V accessory sockets look like cigarette lighter sockets, but they aren't, and the differences are pretty important.

Cigarette lighter sockets in a car dashboard.
Car Culture ® Collection / Getty

Accessory Sockets Aren't Cigarette Lighters

After decades of cigarette lighter sockets that play double duty as accessory sockets, it's only natural to wonder what, if any, difference there is between these two components. While this might seem complex, it's actually not. In basic terms, cigarette lighter sockets are accessory sockets, but accessory sockets aren't necessarily cigarette lighter sockets. It's like how all squares are rectangles, but not all rectangles are squares.

Digging in a little deeper, the issue is that there are two slightly different standards for these sockets. And while they both work with 12V plugs, receptacles that meet the newer of the two standards will not accept cigarette lighters.

Further clouding the issue is that some vehicles ship from the factory with a plug in the cigarette lighter socket. That may seem to indicate that it isn't a cigarette lighter at all, but that isn't the case. When one of these sockets is located in the dash, and there isn't a second one clearly marked as an accessory socket then, chances are it’s probably just a cigarette lighter socket that didn’t come with the lighter portion.

Cigarette Lighters vs. Accessory Sockets

The crux of the issue here is that cigarette lighters weren’t originally designed to provide power to accessories. In fact, the very first cigarette lighters in cars really weren’t suited to that purpose at all. These early lighters used a “coil and reel” system, and it wasn’t until so-called “wireless” lighters hit the market that cigarette lighters gained the dual purpose that they enjoy today.

The consequence of the fact that cigarette lighter sockets weren’t actually designed to provide accessory power means that they aren’t terribly well suited to the purpose. In fact, the purpose that they are suited to, which is heating a bimetallic coil until it is bright, cherry red, is basically the exact opposite from what you’d like to see out of an efficient power transfer system.

The upshot is that since cigarette lighters are designed to get incredibly hot, it doesn’t really matter that their basic design provides a less-than-ideal electrical connection.

When Cigarette Lighter Sockets Became Something More

There are a handful of different cigarette lighter standards in the world, but the one used in the United States is ANSI/SAE J563. Since this standard describes measurements like the diameter of the receptacle, accessory manufacturers are able to make power plugs that have a relatively snug fit, and the slack is taken up by spring-loaded contacts.

However, the standard also includes a second set of measurements that automakers can use for dedicated accessory sockets. Sockets that conform to this standard are slightly different, in that they won’t accept cigarette lighters, but they will accept 12v power plugs from chargers, inverters, and other devices.

Is It a Cigarette Lighter Socket or 12V Accessory Socket?

Unless you want to look up the specs and get out a micrometer, the best way to find out whether you’re dealing with a cigarette lighter socket or an accessory socket is to check your owner’s manual or contact the dealership. The two do look slightly different, but it's a difference measured in millimeters.

You also can’t tell whether or not a socket is designed to work with a cigarette lighter simply based on the fact that it didn't come with one. While most dash-mounted sockets are still designed to accept cigarette lighters, you shouldn't just assume that it does.

The general rule of thumb is that if your dash has multiple sockets, one of them will usually be a cigarette lighter, and the others will probably be accessory sockets. In that same vein, additional sockets located under the dash, in the center console, and elsewhere in the vehicle, are usually dedicated accessory sockets. However, it's a bad idea to just stick a cigarette lighter into any old receptacle based on a rule of thumb. The only way to know for certain is to check with your local dealer or the manufacturer.

Does the Difference Really Matter?

In terms of powering accessories and devices, like your cell phone, there is functionally no difference between cigarette lighter sockets and accessory sockets. If you aren't sure which one you're dealing with, you should feel free to plug into any or all of them to suit your power requirements.

The only important difference is that you can't, or at least shouldn't, plug a cigarette lighter into an accessory socket. In the best-case scenario, nothing will happen at all. In a worst-case scenario, the lighter will heat up, but the socket won't be able to withstand the extreme heat of the lighter.

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