Electric cars use two types of heating mechanisms, namely:
- Resistance heating
- Heat pumps
Let’s look at each of these heating processes in more detail.
Resistance Heating
In some early models of electric cars, the heaters work based on the concept of resistance heating, the same principle applied in ordinary electric space heaters.
Resistance heating is the process of passing an electric current through a resistive element like a coil of wire to generate heat. As the resistive element gets hotter, it heats the air around it too.
Think of this heating method as having your household space heater built somewhere into your electric vehicle. While the resistive element heats up, the car’s fan system blows air over it, and in the process, the air warms up. This heated air is then dispersed throughout the cabin of your car.
Resistance heating is fairly swift, so it tends to warm up the car’s cabin quickly.
To differentiate how heaters work, I also wrote an article to explain how heaters work in Teslas specifically. Their engineering is something special and I thought necessary to dedicate an entire article just for Teslas. Check it out!
Why the Use of Resistance Heating Declined
For a long time, resistance heating was the main method of warming up the cabin in electric vehicles. However, many car manufacturers have now migrated to alternative heating techniques.
Let’s examine why resistance heating became less appealing to electric vehicle users and manufacturers.
The Tug of Energy
In resistance heating in an electric vehicle, the electric current used to heat the resistive element is drawn from the car’s batteries – the same batteries used to power other systems within the vehicle.
Resistance heating requires a considerable amount of electrical power. The majority of the car’s battery power is directed towards heating up the cabin, while the little energy that remains is shared amongst the car’s remaining systems. As a result, your batteries become depleted much faster, and you’d need to charge your car more often.
This tug of energy is the only downside to the resistance heating method. Still, the reduced battery performance that comes with this heating mechanism outweighs the benefits that it can offer a car owner.
Vehicles That Use Resistance Heating
Here are a few car models that make use of the resistance heating method:
- BMW i3 with Range extender
- Generation 1 Nissan leaf and the newer Visia Leaf
- Fluence/Kangaroo
- Ampera
- iMiev+clones
However, because of the resistance method’s high appetite for power, electric vehicle manufacturers have moved towards heat pumps as an alternative cabin heating technique.
Heat Pumps
Heat pumps are a more widely embraced heating method in electric vehicles, primarily because of their ability to save on power.
Let’s take a closer look at how heat pumps work.
The Working Principle of Heat Pumps
Unlike resistance heaters, heat pumps don’t generate and give off heat. Rather, they absorb heat from one place, then transfer that heat to the desired location.
So when it comes to an electric car, heat pumps draw heat from outside the cabin – even when the weather is cold – and direct it into the car to warm you up.
You might be wondering how heat pumps can extract heat from cold air. Well, heat pumps work on the principle that all temperatures above absolute zero carry heat. So no matter how icy the air outside seems, in reality, there’s actually a little bit of heat in it.
Electric cars use a heat pump known as an air source heat pump, which essentially works like a reverse air conditioner. So rather than absorbing warm air and providing cool air like an air conditioner does, an air source heat pump will take in “cold” air, extract the heat from it and disperse that heat into your car’s cabin.
The efficiency of the heat pumps depends primarily on the weather conditions outside the car. The lower the temperatures outside, the harder and longer the pump must work to achieve the desired heating effect.
Reasons Why Heat Pumps Are Preferred Over Resistance Heating Mechanisms
Heat pumps have grown in popularity over resistance heating for the following reasons:
- Heat pumps don’t use as much electrical power as heat resistance elements. It’s estimated that heat pumps use 50% less electrical power than resistance heating elements. Heating pumps save power because they don’t generate heat but instead absorb heat from the air outside.
- Heat pumps can be controlled using an electric car’s manufacturer app. With the technological advancements that have been made in the automobile industry, you can defrost your car and raise the cabin’s temperature remotely using manufacturer apps.
- Heat pumps can improve an electric car’s performance. It’s not only outside air that heat pumps can absorb heat from: they can also pull excess heat generated by the car’s batteries, which in turn helps improve the car’s overall performance.
The Downside To Heat Pumps
Heat pumps are not very efficient in extremely cold weather conditions.
Imagine the air outside is around 45°F (7°C), and you’re tasked with rubbing your hands until their temperature is above 86°F (30°C). You’d need to rub your hands very hard and for a long time to achieve the required heat. The same concept applies to heat pumps as they try to heat your car in the winter.
Although heat pumps don’t use as much battery energy as resistance heaters, they still compete with other car functions for power.
Moreover, an electric vehicle’s driving range significantly lowers in cold weather. A study conducted by the AAA in 2019 revealed that the distance an electric vehicle could drive with the energy stored in its battery was reduced by about 12% when outside temperatures dropped from 70°F to 20°F (21°C to -6°C). So you need to be a little more mindful of your battery when using the heating in your electric car during the winter.
In cold weather, electric cars with smaller batteries will likely lose power faster due to the heat pumps’ energy consumption. On the other hand, this energy-sapping effect is less significant in electric vehicles with larger batteries.
Comparison Between Resistance Heating and Heat Pumps
Below is a table comparing resistance heating and heat pumps in terms of functionality and usage:
| Resistance heaters | Heat pumps | |
| Source of heat | Resistive element | Outside air |
| Power usage | High | Moderate |
| Usage | Diminishing | Wide adoption |
| Some car models in which they are found | Fluence/Kangaroo Ampera and iMiev+clones | Kia Soul EV (1st Gen) Volkswagen e-Golf Nissan Leaf |
Here’s a video from Transport Evolved that gives an in-depth look into how resistance heaters and heat pumps in an electric car function in cold weather:
With the newer electric cars, heating has only a marginal impact on battery power, so you can still achieve both comfort and good driving range in cold weather. However, given that heat pumps are generally less power-consuming than their resistance heating counterparts, I’d recommend an electric car heating system that uses heat pumps.
Safety Analysis
Now that we know how the heaters in electric cars work, let’s debunk a few myths and examine the facts of the health implications of the heated air inside the cabin.
Myth: Air Vents in an Electric Car Release Toxic Emissions When Exposed To Heat
This myth is based on the assumption that the air vents in an electric vehicle are made of plastic. The concern is that as hot air heats the air vents as it passes through, it causes the vents to release trace amounts of chemical compounds that are toxic when inhaled.
However, there is little truth to this myth because an electric car’s air vents are not made of plastic.
Myth: Car Ventilation Systems Expose Passengers to a Hazardous Compound Called Benzene
A common concern with car heaters is the risk of exposure to toxic and carcinogenic emissions.
One myth states that ventilation systems in all cars expose passengers to benzene, a chemical compound that can be toxic after long-term exposure.
While benzene exposure is known to have long-term side effects such as cancer and respiratory complications, there is no substantive link so far between car ventilation systems and benzene exposure.
Fact: Too Much Heat in the Cabin Can Cause Burns
Excessive heat inside your electric car’s cabin can cause skin injuries that are similar to burns.
Known as “toasted skin syndrome”, these injuries aren’t actually burns, but they are caused by exposure to heat.
“Toasted skin syndrome” causes skin discoloration, rashes, or both on the affected area. While the condition is not a major cause for concern, it’s worth avoiding it by using your car’s heater for short periods of time and in a comfortable setting.
