Window Tint Guide: Compare
Ceramic Tint Heat Claims: What the Numbers Really Mean
Shop for ceramic tint for ten minutes and you will see heat numbers everywhere: up to 99% UV, up to 88% infrared, 60% heat rejection. They sound like they measure the same thing. They do not, and the gap between them can be 30 points or more on the very same roll of film.
This guide takes one manufacturer's published spec sheet and walks through what each number means, why the biggest number is usually the least useful, how lab conditions differ from a car parked on an Upstate asphalt lot in July, and what to ask so you compare films on equal terms.
The short answer
Most ceramic tint heat claims quote infrared rejection, which only covers part of the sun's energy and often only part of the infrared band. The number that best predicts how much cooler a car feels is total solar energy rejected (TSER). On LLumar's published sheet, one ceramic film lists 87% selective IR rejection but 54% TSER. Compare films by TSER at the same shade, measured the same way.
Key points
- TSER covers visible light, infrared and UV together, so it is the best single number for comparing heat performance.
- Infrared figures are always larger than TSER for the same film, because infrared is only part of the solar energy that reaches you.
- "Up to" usually means the darkest shade on lab glass; lighter shades of the same film reject less heat.
- Lab numbers are measured on single clear glass, not your car's laminated or factory tinted glass, so treat them as a way to rank films, not a forecast of cabin temperature.
- UV blocking is nearly identical across quality films (LLumar lists more than 99% on every film on its automotive sheet), so it should not decide between them.
The problem
Why heat claims look so different
Sunlight reaching your car is a mix of ultraviolet, visible light and infrared. Each carries part of the energy that heats the cabin. A film can be measured against all of it together, against infrared only, or against a narrow slice of infrared, and each test produces a different percentage.
None of those numbers is false. The trouble starts when a figure measured one way is set next to a figure measured another way, or when a single big number is printed without saying what it measures. A film advertised at 88% can perform worse in your car than a film advertised at 60%, if the first number is infrared at one wavelength and the second is total solar energy.
The fix is not to distrust every number. It is to know which number you are looking at and to compare like with like.
Definitions
The four numbers on a tint spec sheet
- TSER (total solar energy rejected)The one to compare
- The share of all incoming solar energy (UV, visible and infrared) that the glass and film keep out, including heat the film absorbs and re-radiates outward. It is the closest single number to what you feel on your arm.
- IRER (infrared energy rejection)Infrared only, but complete
- LLumar describes IRER as a more complete measure of infrared heat across 780 to 2,500 nanometers, counting absorbed and re-radiated energy. Useful, but it ignores the heat carried by visible light.
- SIRR (selective IR rejection)Usually the biggest number
- LLumar defines SIRR as solar infrared that is not directly transmitted through the glass. It does not count heat the film absorbs and later passes inward, so it reads high.
- IR rejection at one wavelengthTreat with care
- Some marketing quotes blocking at a single infrared wavelength, often measured with a handheld demo lamp. It can be near 100% on a film that still lets plenty of total heat through. Reading a full spec sheet
Worked example
One film, three heat numbers
LLumar publishes performance data for its automotive films on a single sheet, which makes the point clearly. Its IRX 35 ceramic film lists 39% visible light transmission, 54% total solar energy rejected, 60% infrared energy rejection and 87% selective IR rejection. All four describe the same film on the same glass.
If a seller quoted only the 87%, a buyer comparing it against another film's 54% TSER would think the first film rejects far more heat. In reality the two numbers would match exactly. That is why the first question about any heat claim is: which measurement is this?
The same sheet lists LLumar's ATC 35 color-stable dyed film at 35% TSER and 29% selective IR rejection, and CTX 35 ceramic at 48% TSER and 69% selective IR rejection. Measured the same way, the step from dyed to entry ceramic to advanced ceramic is real but smaller than the infrared figures suggest.
LLumar product names are used here to explain LLumar's published data. They are not a statement of which films any shop stocks.
"Up to"
What "up to" usually hides
An "up to" heat figure is almost always the best result in a product line: the darkest shade, on clear lab glass. On LLumar's sheet the 5% versions of its films carry the highest TSER figures, while lighter shades of the same film are lower. A 5% film is far below what South Carolina allows on a car's front side windows, so the top number often describes a version you could not legally put where you sit.
Advanced ceramic narrows that gap. LLumar's IRX keeps its infrared figures nearly flat from 5% to 50%, while TSER drops from 62% to 50% as the film lightens. That flat infrared line is the real selling point of a good ceramic film: you can choose a legal shade and keep most of the infrared rejection.
Regulators take "up to" seriously in other window products. In 2012 the Federal Trade Commission settled with five replacement window sellers over energy savings claims, and the orders required each company to back "up to" savings claims with evidence that all or almost all consumers would get the maximum savings. Tint is a different product, but the lesson carries over: an "up to" number is a ceiling, not a typical result.
Lab vs car
Why your car will not match the lab
LLumar's sheet notes that its data was captured under NFRC guidelines on a single pane of quarter-inch clear glass, and that actual performance will vary with glass type. Car glass is different. Side windows are often tempered glass that may already carry a factory tint, rear glass on many SUVs is dark privacy glass, and the windshield is laminated.
Cabin temperature also depends on things no film controls: paint color, the size of the glass roof, which way the car is parked, how long it sits and whether the windshield is treated. A film with 54% TSER does not make a cabin 54% cooler. It cuts the solar energy entering through the windows it covers, by roughly that share under lab conditions.
Lab numbers still matter. Measured the same way, they rank films reliably, and that ranking holds in the car even when the absolute figures shift.
Coverage
Which windows the claim applies to
Heat rejection only happens where film is installed. Tinting the two front side windows helps the driver and front passenger, especially on the sun side of a commute. A full car adds the rear doors and back glass. Many tint packages exclude the windshield, which is the largest piece of glass in most cars, because South Carolina only allows film above the AS-1 line there.
So a high TSER film on two windows can feel less effective than a moderate film on every window. When comparing quotes, compare the film and the coverage together.
How to compare
A fair way to compare heat claims
Ask for TSER
Request total solar energy rejected for the exact film and shade you would buy, not the product line's best result.
Match the shade
Compare films at the same visible light transmission. A darker film rejects more visible light, which raises TSER regardless of technology.
Check the test basis
Spec sheets should say how and on what glass the data was measured. Two sheets measured differently cannot be compared directly.
Ignore lamp demos
A heat lamp and a hand behind the glass is a demonstration, not a measurement. It usually highlights infrared only.
Set UV aside
Quality films all list near-total UV blocking, so UV is a minimum to confirm, not a reason to pick one film over another.
Decide on value
Price the heat difference over the years you will own the car, not the size of the advertised number.
| Film (LLumar) | Type | Visible light | TSER | Selective IR rejection |
|---|---|---|---|---|
| ATC 35 | Color-stable dyed | 38% | 35% | 29% |
| ATR 35 | Metallized | 37% | 44% | 53% |
| CTX 35 | Ceramic | 37% | 48% | 69% |
| IRX 35 | Infrared-rejecting ceramic | 39% | 54% | 87% |
Source: LLumar Window Film Performance Data, 03/26. Actual performance varies with glass type. Shown to explain how heat numbers differ, not as a list of films any shop stocks.
Compare our two films side by side
We install LLumar Carbon (from $125.99) and LLumar Ceramic (from $199.99) for the two front side windows, with full vehicles by quote. Ask us how they differ on heat for your car.
Common questions
Is 99% UV rejection the same as 99% heat rejection?
No. UV is a small slice of the sun's energy, so blocking almost all of it barely changes cabin heat. Most of the heat you feel comes from infrared and visible light. A film can block more than 99% of UV and still reject well under half of total solar energy, which is why TSER is the better heat number.
Why does the infrared percentage go higher than TSER?
Infrared is only part of the solar energy reaching the car, and selective IR figures count only infrared that is not directly transmitted. Ceramic films are tuned to stop infrared, so they score high on that slice. TSER also counts visible light, which a legal-shade film must let through, so it is always lower.
Does a darker film always reject more heat?
Within the same product line, usually yes, because darker film absorbs and rejects more visible light. Between technologies, not always. On LLumar's sheet, a 35% ceramic film lists a higher TSER than a 5% dyed film from its color-stable line. Technology often matters more than darkness.
Can I test a tint's heat rejection myself?
Not accurately. Heat lamps and handheld meters at a counter usually show infrared at a narrow band and exaggerate differences. You can compare how the car feels on similar sunny days before and after, but the reliable comparison is manufacturer TSER data for the exact film and shade.
Will ceramic tint lower my AC bill or improve mileage?
It reduces solar heat entering through the tinted glass, so the AC has less to remove after the car sits in the sun. How much that saves depends on the car, the coverage and how you drive, and it is easy to oversell. Treat comfort as the main benefit and any fuel saving as a small extra.
Sources
- LLumar Window Film Performance Data (LL0116NAEN, 03/26), Eastman Performance Films (https://llumar.com/content/dam/eastman/performance-films/llumar/documents/LL0116NAEN_AutoSpecs_screen.pdf), accessed October 2026
- Ceramic Window Tint, LLumar (https://llumar.com/en/tint/ceramic/), accessed October 2026
- IRX Ceramic Window Tint, LLumar (https://llumar.com/en/tint/ceramic/irx/), accessed October 2026
- Window Marketers Settle FTC Charges That They Made Deceptive Energy Efficiency and Cost Savings Claims, Federal Trade Commission (https://www.ftc.gov/news-events/press-releases/2012/02/window-marketers-settle-ftc-charges-they-made-deceptive-energy), accessed October 2026
- S.C. Code Ann. § 56-5-5015, South Carolina Legislature (https://www.scstatehouse.gov/code/t56c005.php), accessed October 2026
- Automotive Window Film and Your Car, International Window Film Association (https://iwfa.com/automotive/), accessed October 2026
Prices on this page are The Auto Show’s published starting prices. Film ratings and warranty terms come from the manufacturer. This guide explains South Carolina law in plain words; it is not legal advice.