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

Driving a cold car in the dead of winter isn't any fun, and it can even be dangerous if you aren't able to adequately defrost the windows. One of the easiest, and most attractive, solutions is to plug a heater into the cigarette lighter socket, but is anything ever really that easy?

Do Portable Cigarette Lighter Car Heaters Work?

Cigarette lighter heaters work, in that they take energy from a car’s electrical system and turn it into heat energy, but they have some pretty hard limitations.

The problem is that there is a huge gulf between a device that technically accomplishes, sort of, the task it was designed to perform, 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.

The wiring that connects cigarette lighters and accessory sockets to power is typically also on the lightweight end of the spectrum, so simply installing a beefier fuse is not a solution worth entertaining.

Even the best electric car heaters have limits, but cigarette lighter heaters are especially limited due to these wiring and fuse issues.

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.
    • Pros: This allows you to use an appropriate wire gauge for a high current draw, and install an in-line fuse to properly protect the new circuit.
    • Cons: 12 V car heaters, even ones designed to be wired directly in this manner, still tend to be pretty weak.
  • Install an inverter and use a residential space heater.
    • Pros: This allows you to use a more powerful heater. Even the smallest residential space heater is capable of heating up the interior of a car or truck.
    • Cons: Residential space heaters take a lot of power to run, and your charging system may not be equal to the task.

Either of these will work if done properly, and neither one is necessarily better than the other. Wiring a 12 V 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.

It's important to remember that these solutions still can't adequately replace a functional factory heater that relies on heat transfer from engine coolant.