The main issue is that drivers often look to plug-in heaters to replace or augment a factory heating system that has stopped working, and that’s a kind of heat output that just can’t be matched due to the inherent limitations of plug-in car heaters.
Types of Plug-in Car Heaters
There are two main plug-in car heater options available, and they are not created equal.
120 V residential space heaters: These are electric space heaters are designed to plug into the wall. The ability of these devices to put out heat is limited only by size, and big electric space heaters are capable of heating up much larger spaces than the interior of a car. Many heaters in this category aren’t safe for use in confined spaces, and none of them is portable.12 V portable car heaters: These are also electric space heaters, but they run off the 12 V DC power that’s available in your car. These heaters are primarily limited by the amount of amperage that they can safely draw from the limited resources available from your vehicle’s electrical system. The heat output won’t ever come close to matching a factory heating system.
Within these two basic categories, there are a number of subtypes, including:
Radiative heatersHalogen heatersCeramic infrared heatersConvective heatersOil heatersWire element heaters
Some of these heaters are suitable for use in confined spaces like cars, and others are not. The main concerns are that some of these heaters are more prone to causing fires when placed in close proximity to flammable materials, and some are unsuitable to small enclosed spaces due to consuming or displacing available oxygen.
120 V Plug-in Car Heaters
The largest category of plug-in car heaters is made up of both residential space heaters that happen to be small enough and safe enough to use in confined spaces and also 120 V heaters that are specifically designed for use in cars, recreational vehicles, and similar applications. Since automotive electrical systems typically provide 12 V DC instead of 120 V AC, these heaters typically can’t be used in unmodified vehicles. The two basic options for using a 120 V plug-in car heater are to install a car power inverter or to use an extension cord. The first option allows a 120 V heater to be used when the engine of the vehicle is running, and the second option allows one of these heaters to be used when the vehicle is parked.
Using a 120 V Plug-in Heater With an Inverter
The only way to use a 120 V plug-in space heater as a replacement for the factory heating system is to install an inverter. The inverter may be wired directly to the battery or plugged into a 12 V accessory socket, but most space heaters draw far too much amperage to be used with cigarette lighter inverters. When using a 120 V plug-in car heater with an inverter, it’s important to remember a few things: If the primary goal of using a plug-in heater in a car is to heat it up prior to driving it, then plugging it into the vehicle’s electrical system with an inverter is not the best solution. In that case, it’s almost always going to be a better idea to run an extension cord to the vehicle from a convenient outlet. In cases where the factory alternator isn’t capable of putting out enough amperage to handle the load from a powerful heater, it may be necessary to install a high output alternator. For high-wattage space heaters that are truly capable of matching the heat output of a normal automotive heating system, running off an inverter is unlikely to work at all.
Using a 120 V Plug-in Heater Without an Inverter
If the primary goal of using a plug-in heater in a car is to simply warm up the interior prior to driving the vehicle, then an extension cord is a much better solution than an inverter. In especially cold areas where vehicles are commonly equipped with block heaters, it’s typically even possible to gang an additional outlet to the block heater connection, which provides an easy way to plug in a 120 V space heater. In situations where a vehicle doesn’t have a block heater, there is sometimes enough of a gap to close an extension cord in one of the doors. If that isn’t possible, then the best way to obtain access for an extension cord is typically through the firewall, although that usually involves drilling a hole and safely routing an extension cord through the engine compartment.
12 V Portable Car Heaters
Unlike 120 V space heaters, 12 V portable car heaters are specifically designed for automotive use. That means they’re typically safe to use in confined spaces, and they can be connected directly to the electrical system of a vehicle without the need for an inverter. Of course, all “plug-in” 12 V car heaters use a cigarette lighter socket plug, which means they are inherently limited in wattage. That means most of these units can only put out a very limited amount of heat. In situations where more heat is desired, it’s necessary to either use a 120 V plug-in heater or to wire a more powerful 12 V heater directly to the vehicle’s battery. Since 12 V heaters that are wired to the battery aren’t limited by the low amperage nature of cigarette lighter and accessory socket circuits, they can be much higher in wattage. Unfortunately, the only solution to a broken car heater is to fix the heater or install a true car heater replacement that actually taps into the hot engine coolant just like the factory system. While plug-in car heaters can work fine if you temper your expectations, both types suffer from too many drawbacks to ever serve as true replacements.
