The only number that matters: TSER
Total Solar Energy Rejected (TSER) is the percentage of the sun's full energy spectrum — ultraviolet, visible, and infrared combined — that the glass-and-film assembly keeps out of the room. It is the honest, whole-picture figure.
A film rated 60% TSER on clear single-pane glass rejects 60% of the total solar energy striking that window. Everything else you see on a spec sheet is a component of, or a distraction from, this number.
Why 'blocks 99% of infrared' is a misleading headline
Infrared rejection numbers are often quoted at a single wavelength — commonly 950 nanometres — where films perform best. Near-infrared runs from about 780 to 2,500 nm, so a single-point reading is not representative.
Worse, infrared is only about 53% of total solar energy. A film that rejected 99% of infrared and nothing else would still have a TSER around 52%. Always ask for TSER across the full spectrum, not an IR headline.
SHGC and the Title 24 connection
Solar Heat Gain Coefficient (SHGC) is TSER's inverse, expressed as a decimal: the fraction of solar energy that gets through. A 0.28 SHGC assembly transmits 28% and rejects 72%.
California's Title 24 energy code specifies SHGC targets rather than TSER, which is why energy consultants and commercial specifications almost always speak in SHGC. Converting is simple: SHGC ≈ 1 − TSER.
Typical heat rejection by film type
- Dyed film: 30-45% TSER — noticeable glare relief, modest temperature change
- Metallized film: 45-65% TSER — strong heat rejection with reflective appearance
- Ceramic film: 50-65% TSER — strong rejection, neutral look, no signal interference
- Nano-ceramic / spectrally selective: 55-70% TSER at high visible light transmission
- Dark reflective commercial film: 70-80% TSER — maximum rejection, significant appearance change
- Clear safety film with solar layer: 40-55% TSER depending on construction
What the numbers feel like in a real Los Angeles room
On a 92°F September afternoon, an untreated west-facing living room in the San Fernando Valley commonly runs 84-88°F at 4pm even with the air conditioning running, and surfaces in direct sun measure 110-125°F.
With a 60-65% TSER ceramic film, the same room typically settles 6-9°F cooler at peak, and directly sunlit surfaces drop 25-35°F. The subjective change most homeowners describe is not 'the room is cold' but 'the sun stopped pushing on me' — the radiant load on skin disappears.
The second, quieter effect is that the air conditioner stops short-cycling to fight one hot room, so the whole floor equalizes and the thermostat setpoint becomes achievable.
How to read a manufacturer spec sheet
- Check which glass the number was measured on — single-pane clear, double-pane clear, and Low-E give very different results for the same film
- Compare TSER to TSER, never TSER to IR rejection
- Note visible light transmission (VLT) alongside TSER; high TSER at high VLT is the expensive, impressive combination
- Look at glare reduction if squinting at screens is the actual complaint
- Confirm the U-factor if winter heat retention matters for the project
What window film cannot do
Film addresses solar gain through glass. It does not address heat conducted through walls and roofs, air infiltration around old frames, or heat already stored in the building's mass. A room that stays hot after sunset has a conduction and infiltration problem, not a solar-gain problem, and film will disappoint there.
Related reading and services
Frequently Asked Questions
How many degrees cooler will my room be with window film?
For a sun-exposed room with a 60%+ TSER film, expect a 6-9°F drop at peak afternoon and a 25-35°F drop on directly sunlit surfaces. Rooms with modest sun exposure see smaller air-temperature changes but still lose most of the radiant discomfort.
What is a good TSER percentage for a home?
For Los Angeles homes, 50-65% TSER is the practical sweet spot. Above that you generally have to accept a darker or more reflective appearance, and below about 45% the comfort change becomes hard to notice on west-facing glass.
Does darker film always block more heat?
No. Darkness measures visible light, not total energy. A high-end spectrally selective film at 70% visible light transmission can outperform a cheap dyed film at 20% VLT on total solar energy rejected.
Does window film help in winter?
Standard solar film slightly reduces winter solar gain, which is usually irrelevant in Southern California. Low-E window film is the product designed to also reduce heat loss through glass, and it is the right specification in climates with real heating loads.
Will window film lower my air conditioning bill?
In cooling-dominated climates yes, typically in the range of 5-15% of total cooling cost depending on glass area, orientation and film performance. The comfort improvement is usually more noticeable than the line item on the bill.
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