When you’re in the market for window tinting, the first thing you notice is the darkness of the film. You see a car with a “20% tint” and think you know exactly what you’re getting. But a number of percentages on a spec sheet are far more important than how dark the film is. These are VLT, TSER, and IRR, and they are the key to understanding how a film will truly perform.  

Instead of focusing on just the aesthetic of the film, a savvy car owner in a sunny climate needs to understand what these terms mean and why they matter. We’re going to break them down in simple terms so you can make an informed decision that prioritizes comfort and performance, not just privacy. 

VLT: Visible Light Transmission 

This is the easiest number to understand because it’s what you can see. VLT stands for Visible Light Transmission, and it measures the percentage of visible light that passes through the film and into your car.  

• A high VLT (e.g., 70%): Means the film is light and clear, allowing most of the visible light to pass through.  

• A low VLT (e.g., 5%): Means the film is very dark, only allowing a small amount of light to pass through. This is often referred to as “limo tint.”  

This number is crucial for balancing your desire for privacy with your need for safe visibility, especially at night. It’s also the number that is regulated by local window tinting laws, so it’s important to know the legal limit in your area. 

TSER: Total Solar Energy Rejected 

TSER is arguably the most important number on a spec sheet, as it gives you a comprehensive picture of how well a film performs at keeping your car cool. It stands for Total Solar Energy Rejected, and it measures the total percentage of solar energy—including visible light, infrared, and ultraviolet light—that the film blocks.  

Think of it as the overall grade for the film’s performance. A film with a high TSER (e.g., 60-70% or more) will keep your car significantly cooler than a film with a low TSER, regardless of how dark it is. 

IRR: Infrared Rejection 

IRR stands for Infrared Rejection, and it’s the hidden hero of a great tint. Infrared light is a form of solar energy that you cannot see, but you can feel it as heat. In fact, infrared light is responsible for a large portion of the heat you feel in your car.  

A film with a high IRR (e.g., 90% or more) is specifically engineered to target and block this heat, which is why modern nano-ceramic films can be almost clear yet still provide superior heat rejection to a much darker, dyed film. A high IRR rating means you get all the benefits of a cooler car without having to compromise on a dark aesthetic or nighttime visibility. 

The Takeaway: It’s All About the Balance 

When choosing your window tinting solution, don’t get fixated on a single number. Instead, consider how VLT, TSER, and IRR work together to meet your specific needs. You can choose a film with a high VLT (lighter film) but still get a high TSER and IRR for maximum heat rejection. Or you can choose a low VLT for ultimate privacy, knowing that a high TSER and IRR will ensure your car stays cool.  

A quality film, like a modern nano-ceramic tint, offers a perfect balance of all three metrics, giving you the best of all worlds: a film that is legally compliant, keeps you cool and comfortable, and provides safe, clear visibility at all times.