Heaters in Electric Cars: How Do They Work?

Driving in the freezing cold without a heater in your car can be downright miserable or even deadly — good reasons why every new car has one. That includes new electric vehicles, even though they lack an engine that typically produces the heat in cars with internal combustion engines. So how do electric cars have heaters, how do they work, and how do they differ from the heaters in gas-powered cars? We'll break all that down in detail right here, and we'll even give you some range-saving tips when it comes to the HVAC system in your EV.

The first thing to know about heaters in EVs is that they differ from the ones found in gas-powered vehicles. Internal combustion engines produce a lot of heat, and some of that heat is directed into the cabin to warm your passengers on a cold winter's morning. Electric cars, of course, don't have engines. So how are their cabins heated?

EVs rely entirely on electricity to produce heat for their cabins, and early electric cars like the original Nissan Leaf and Mitsubishi i-MiEV used resistive heating for this process. (Some modern EVs like the Rivian R1T still do.) The process is fairly simple and works a lot like a space heater you might find in a home. Essentially, electricity is run through a conductor to produce heat. Air is then blown through the heating element and into the cabin and, just like that, an EV has heat. But resistive heating uses a lot of energy, and running the heater, in conjunction with colder exterior temperatures, drastically reduces an EV's efficiency and lowers its estimated range.

Positive temperature coefficient heaters work in much the same way that resistive heaters do, but with one key difference. When current is first applied to the heating element, it gets hot quickly, but as the temperature rises, the current pull decreases and the electrical resistance increases to reduce the risk of overheating. Thanks to the reduced current requirement, PTC heaters are more efficient than their resistive heater counterparts.

But there's another heating method that's becoming more popular in modern electric cars: the heat pump. Heat pumps are nothing new — the Nissan Leaf, for instance, has used a heat pump since 2013 — but not every new EV uses one, and they are far more efficient than either resistive or PTC heaters. Heat pumps work a lot like your air conditioning does, only in reverse.

Air is drawn from the outside and run through a condenser that contains refrigerant. The refrigerant is compressed and that creates heat. The hot air is then pumped into the cabin to warm it up. The reason heat pumps are a favorable alternative to traditional resistive heating is twofold. The first is that heat pumps can also help cool down the car, serving as an air conditioner as well. Additionally, the process is more efficient than resistive heating and puts less strain on an EV's battery and reduces the range penalty an EV takes when heating up.

Regardless of how efficient the heater is, using it will hurt your EV's range simply because power is needed to operate it. However, because heaters are used when it's cold, and cold weather by itself is enough to degrade range significantly, EV drivers need to deal with two factors negatively impacting range.

All extreme weather conditions are bad for an EV's range and overall performance, but very cold climates are especially detrimental. An electric car's battery uses chemical reactions to store and release the energy that's used to power the vehicle, and extreme cold slows down these reactions. The result is a battery that is far less efficient in colder conditions because they have to work harder than in a more temperate climate.

Electric cars have systems that help regulate a battery's temperature to try to keep the battery at an optimal operating temperature, but these systems also consume energy. At very low (think at or just below freezing) temperatures, it takes plenty of power to keep an EV's battery at a stable temperature. Range loss is guaranteed in cold weather, but EVs differ vastly in how much range they lose.

An ongoing research project conducted by Recurrent examines how 7,000 different EVs react to cold weather. The results show that all lose some range, but that the range lost heavily depends on the car itself. The entire Tesla model range was tested, and Teslas tend to lose between 13% and 18% of their overall range in freezing weather when compared to 70-degree weather. The Ford Mustang Mach-E and Volkswagen ID.4 both had a confirmed range loss of 30%.

Another small but significant factor in an EV's range has to do with tires. Electric vehicles often come on tires that have a lower rolling resistance than vehicles with internal combustion engines. The reason is so that the EV has to do less work to unstick the tire from the road surface to get the car moving. Winter tires, which are designed to increase traction to deal with slippery surfaces, have a much higher rolling resistance than standard tires. As a result, electric motors have to use more energy to get the car rolling, and this too can hurt range.

If you live in a colder environment, there are ways to minimize the impact that using your car's heater will have on your overall range. If you are able to keep your EV in a garage, turn the car on and warm it up there while it's charging. This will allow the car to come up to your desired temperature before you ever take it off the charger, and it won't force the car to use its battery's energy to heat up in colder weather because it's being fed by the charger. A number of EVs allow you to activate a warm-up from your smartphone, like the Ford Mustang Mach-E and the Hyundai Ioniq 5.

Another tip is not to forget about the other heating addenda in your car. Heated steering wheels and heated seats draw power, but they aren't nearly as detrimental to your overall range as heating up the car's entire cabin is. Consider using these features to keep yourself warm after bringing the interior to a livable temperature to prevent your EV from continually drawing power to warm the cabin.

Until battery manufacturers come up with a major breakthrough, there will always be the need to balance a heater's energy requirements with the desire to be comfortable inside the cabin. It's worth keeping in mind that colder temperatures mean you simply have to be more careful and think further in advance about your journeys when you're in an EV. Some EVs even feature special modes that do their best to preserve range and minimize the toll HVAC systems take on batteries. If you live in an environment that frequently gets near or below freezing temps, looking for an EV with battery-saving software built in might be a good idea, too.