Short answer
Total solar energy rejected (TSER) is the share of the sun’s total energy, including visible light, infrared and ultraviolet, that filmed glass keeps out of a room. A film with 60% TSER keeps out 60% of the incoming solar energy. It is the best single number for comparing heat control between films, as long as both values are quoted on the same glass. TSER is roughly 1 minus the solar heat gain coefficient (SHGC).
What’s in sunlight
Sunlight reaching the ground is roughly half infrared (felt as heat), a little under half visible light, and a few percent ultraviolet. All three carry energy into a building. A film that blocks only one part leaves the rest coming in.
How TSER works
When sunlight hits filmed glass, part is reflected, part is absorbed by the glass and film, and part passes through. The absorbed part warms the glass and is released to both sides. TSER adds the reflected energy to the share of absorbed energy that flows back outdoors.
The other numbers on a spec sheet
| Number | What it means | Better is… |
|---|---|---|
| VLT (visible light transmission) | Share of visible light that passes through | Depends: higher for daylight, lower for glare |
| TSER | Share of total solar energy kept out | Higher |
| SHGC | Fraction of solar heat that gets in, 0 to 1 | Lower |
| Shading coefficient | Older measure of solar heat gain relative to clear glass | Lower |
| UV rejection | Share of ultraviolet blocked | Higher; most films are 99%+ |
| Visible light reflectance (exterior / interior) | How mirror-like the glass looks from outside and inside | Depends on the look you need |
| Glare reduction | Reduction in visible light compared with the unfilmed glass | Higher cuts more glare |
| U-factor / emissivity | How readily heat flows through the glass by conduction and radiation | Lower insulates better |
Why infrared rejection can mislead
Many spec sheets quote a high “IR rejection” figure. It is often measured over a narrow band of infrared wavelengths, not the whole infrared range, and it ignores the energy in visible light. A film can have an impressive IR number and a modest TSER. When the question is heat, TSER and SHGC are the numbers to use.
Light-to-solar-gain ratio
If you want daylight without heat, divide VLT by SHGC. This light-to-solar-gain (LSG) ratio shows how much daylight a film lets in for the heat it admits. The U.S. Department of Energy describes glazing with an LSG of 1.25 or higher as spectrally selective.
A worked example
Two hypothetical films, values made up for illustration only, on the same clear glass:
| Film A | Film B | |
|---|---|---|
| VLT | 70% | 20% |
| SHGC | 0.45 | 0.30 |
| TSER (about 1 − SHGC) | 55% | 70% |
| LSG (VLT ÷ SHGC) | 1.56 | 0.67 |
Hypothetical values to show the arithmetic, not data for any real product.
Film B keeps out more heat, but it’s dark. Film A keeps out a bit less while letting in more than three times the daylight, which is what a spectrally selective film is for. Neither is “better” until you know whether the room needs daylight, glare control or maximum heat rejection.
Why the glass changes the numbers
Film makers usually publish values for the film on a reference glass, commonly clear single pane. On tinted, insulated or low-e glass, the values change, and the film’s added benefit is usually smaller because the glass already does part of the work. Ask for data on your glass type, and for the film-to-glass check that confirms the film is safe on it.
How to compare two films
- Make sure both sets of numbers are quoted on the same glass
- Compare TSER (or SHGC) for heat, not IR rejection
- Check VLT against how much daylight and glare control the room needs
- Check exterior reflectance against building or association rules
- Check interior reflectance if people work after dark
- Ask for the manufacturer’s data sheet, not a summary
Talk to Texas Tinted
Not sure how to read the spec sheets you’ve been given? We’ll compare films for your glass and explain the numbers.
Related guides and services
Frequently asked questions
What is a good TSER for commercial window film?
It depends on the goal and the glass. Compare films on the same glass, and balance TSER against the daylight (VLT) and look (reflectance) the space needs.
Is TSER the same as heat rejection?
TSER is the most complete measure of heat rejection because it counts all solar energy. “Heat rejection” in marketing sometimes means a narrower IR figure instead.
How is TSER related to SHGC?
TSER is roughly 1 minus SHGC. A film on glass with an SHGC of 0.40 rejects about 60% of solar energy.
Plan your commercial window film project
Tell us about the building and the problem you want to solve. We’ll set up a free consultation and site assessment, then send a written proposal. Prefer to talk? Call or text (832) 492-5314.