I got this question from a Recurrent customer who lives in the Northeast, a region with the potential for extreme temperatures in both winter and summer months. Window tint reduces solar rays – often showing a rating like total solar energy rejected (TSER) – so it is easy to see how tinted windows would reduce the need for indoor climate cooling in the summer and increase overall range.
But what about the cold winter months?
Tinting windows should also be able to help in the winter because the films used to make these tints not only prevent to some degree thermal radiation from entering your car, but should also help prevent thermal energy from leaving the car. The thing to keep in mind is that not all tint films are made the same and they will have a wide range in insulation, UV blocking, and infrared blocking properties.
During the summer, tinted windows will help to reduce the amount that EV drivers will have to run the AC, thus saving battery capacity on that drive. While in the winter, that same tint will prevent your car from warming up from solar radiation (which is a negative), it will also help insulate your car to prevent heat loss from your heating system (which is a positive). The less work the battery has to put into heating your cabin or your body using the seat warmer, the more energy your battery will have for driving.
The extent to which tinted windows help will depend on what percentage of infrared and UV light they block and on how insulating they are. It’s smart to dive into the details by comparing R or U values for insulation properties. A good tint installation provider should be able to provide you with material data sheets for the products they use.
Limited Scientific Studies on Tinting
There are not any scientific studies on EV range in cold weather, at least that I could find. One company claimed that window tints can save up to 10% EV range, but it is hard to validate and companies often report their best results rather than their average results. Therefore, I would expect window tinting can preserve up to 10% EV range in cold conditions, but on most days it will probably be less than that. The amount that you will save will depend on how sunny it is, the temperature outside, your set temperature inside, the degree to which your car windows insulate and prevent infrared and UV radiation from entering the car, and whether or not you are heating yourself with seat warmers or warmed up air from your battery. It’s always good to remember that seat warmers use less energy than heating the cabin air.
Depending on the cost of install and maintenance of window tint, it could be a good investment to reduce the load on your battery. Given that much of EV range in the winter is cut to heat the cabin and heat the battery, I'd imagine more folks should start to think about this, including myself.