Do Cigarette Lighter Heaters Work?

cigarette lighter heater windshield frozen
Cigarette lighter heaters are better at defrosting than they are at heating, and they're really better at demisting than anything else. Jeff Schultz / Design Pics / Getty

Question: Will a car heater cigarette lighter even work?

The heater in my car isn’t working very well, but I don't have enough money to fix it right now. So I’ve seen these car heater cigarette lighter things that aren’t too much money, and I wonder how well they could actually work. If I could use one of those to warm up my car, that would be great. I wonder if a cigarette lighter car heater would even work, though?

Answer:

Cigarette lighter heaters work, in that they take energy from your car’s electrical system and turn it into heat energy, but we're talking about a pretty loose definition of work. The truth is that you would have just about as much luck trying to warm your car up by yelling at it.

The problem is that there is a huge gulf between a device that technically works and one that does any kind of useful work. And when you're talking about a heater that is designed to plug into a cigarette lighter socket, there's a very limited amount of work that you can expect it to do.

When you plug a car heater into a cigarette lighter socket, the output of the heater will automatically suffer from a hard limit based on the wiring, and the fuse, that's connected to the socket. Both cigarette lighters and accessory sockets are wired with relatively low amperage fuses, which puts a hard limit on the wattage of this type of heater.

Even the best electric car heaters have limits, but cigarette lighter heaters are especially limited.

Using a Cigarette Lighter Heater

If you’re looking for an alternative to your factory heater, then a cigarette lighter heater probably isn't going to cut it. These heaters do work, and they do put out heat, but they are better suited to defrosting duty or warming up your hands than actually heating up the air inside your car.

So if all you need is a replacement defroster, you might be perfectly happy with a cigarette lighter heater. Or if it really doesn't get that cold where you live, and you just need a little extra heat to get you by, then this might actually be a viable option.

In most cases, you’ll be better off with a 12-volt heater that’s wired directly to the battery with an inline fuse, or a residential space heater plugged into an inverter, although both of those options are limited by the amount of power that your car’s electrical system is capable of putting out.

If you’re just looking to warm your car up in the morning, then a space heater plugged in via an all-weather extension cord is probably your best bet. It's also possible that a battery operated heater may do the trick if you’re just looking to defrost your windshield.

The only true replacement for a factory car heater is a universal heater that relies on hot coolant rather than an electric heating element, but they are far and away more expensive and difficult to install than cigarette lighter heaters.

The Problem with Car Heaters and Cigarette Lighters

Car heaters that have cigarette lighter plugs are typically very low in wattage due to the limitations of cigarette lighter circuits.

Most of these circuits are wired with 10 or 15 A fuses, which is pretty low. At 12 V DC, even a 200W heater will draw over 16 A, which is enough to pop most cigarette lighter and accessory outlet circuits. Of course, any heater that includes a blower has to dedicate part of its rated wattage to running the fan, which is why a lot of car heaters that plug into cigarette lighter sockets don’t have that feature.

So while you don’t need a huge residential space heater to warm up the relatively small amount of space inside your car, anything that you can plug into your cigarette lighter socket is probably going to leave you cold.

Alternatives to Cigarette Lighter Car Heaters

In order to provide enough power to run an electric heater that can actually warm up the interior of your car, you either have to:

  • wire a 12 V heater into its own circuit
  • install an inverter and use a residential space heater

Either of these will work if done properly, and neither one is necessarily better than the other. Wiring a 12v heater into its own circuit is more efficient than using an inverter, but the wiring in an inverter is a more versatile solution since you’ll be able to use it for more than just an electric car heater. Of course, neither solution is going to be a direct replacement for a functional factory heater that relies on heat transfer from engine coolant.

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