Electric Window Tint: How Smart Tint Works, What It Costs, Is It Legal

"Electric", "smart", "switchable" and "electrochromic" tint are used as if they mean the same thing. They are three different technologies, and the difference decides what you see through the glass.

PDLC (polymer dispersed liquid crystal) film is what most aftermarket smart tint is. Liquid crystal droplets sit in a polymer layer. With no power they scatter light, so the glass looks frosted white or gray, like a shower door. Apply voltage and the crystals line up and the film goes clear. It is a privacy product: it hides the cabin but does not make the view darker the way tint does. Smart Tint sells a reverse version, Flip Tint, that is clear when unpowered and private when powered.

SPD (suspended particle device) glass uses tiny particles in a film between glass layers. Unpowered, the particles block light and the glass is dark. Powered, they align and the glass clears, and the level in between can be varied. This is true dimming, like sunglasses, and the view stays sharp. Electrochromic glass darkens through a chemical reaction when a small voltage is applied. It also dims rather than frosts but changes more slowly than SPD or PDLC. Both are factory glass products, not a film a tint shop applies.

Factory electric tint lives almost entirely in glass roofs, where driving-visibility tint laws do not apply the way they do on front windows.

Mercedes-Benz was the first big name. Its MAGIC SKY CONTROL roof uses SPD glass from Research Frontiers. In a January 2014 filing, Research Frontiers said the roof was on thousands of SL and SLK roadsters and was launching on the new S-Class, that it blocks over 99% of UV, and that Mercedes-Benz test data showed cabin temperatures up to 18°F (10°C) lower than with conventional glass.

Cadillac's CELESTIQ has the largest SPD roof in production, according to its supplier Gauzy, split into four zones so each occupant sets the shade above their own seat. Gauzy says it switches in seconds and blocks up to 99.5% of visible light, 99% of UV and 95% of infrared. The same release lists Ferrari and McLaren among past SPD users. BMW also offers a shading glass roof on the iX, but we could not confirm its specifications on a BMW page, so we leave it out of the numbers here.

You cannot add SPD or electrochromic glass to a car that did not come with it; it is laminated at the factory, and a replacement roof panel is a dealer body-shop job. For a fixed-shade roof film instead, see Tint for a Glass Roof: Heat, Legality and the Films That Work.

Aftermarket smart tint is a PDLC film cut to each window and stuck to the inside of the glass. Each panel has a wired edge, so the job is part tint install and part 12-volt wiring: the leads run through the door, a controller or driver steps vehicle power up to what the film needs, and a switch or remote turns it on. BenQ Materials, for example, specifies 48 volts for its sunroof PDLC, well above a car's 12-volt system, which is why a controller is part of the kit. Ask the shop where the wiring runs, how it is fused, and what happens to the windows when the car is off.

Smart Tint, one of the few brands selling car kits in the US, lists its standard film at $950 to $1,100 for a two-door car, $1,650 for a four-door and $1,950 for a six-door, and states that professional installation is required. Its Flip Tint, clear when unpowered, lists at $1,799 to $1,949 for two doors and $3,499 for four doors. Ask whether a shop's quote includes labor, wiring and the controller, because the list price is for the product.

Gauzy, which supplies factory smart glass, says it currently works only with carmakers and Tier 1 suppliers and plans an aftermarket product later. Few tint shops install smart film, so expect it more often at custom and audio shops.

Factory SPD glass does, at least on paper: up to 95% infrared rejection on the CELESTIQ and a measured cabin temperature drop in Mercedes-Benz tests. Those are manufacturer figures, and they describe the glass when it is dark.

Aftermarket PDLC is a different story. A frosted film scatters light rather than blocking it, so a lot of the sun's energy still comes through. Gauzy says its solar-control PDLC version blocks up to 86% of infrared, and BenQ Materials claims 99% UV and 90% infrared for its sunroof PDLC, but those are factory products, and the car kits we looked at publish no total solar energy rejected (TSER) number at all. Without TSER you cannot compare it fairly to a film like XPEL Prime XR PLUS, which rejects 59% of solar energy at 35%.

If heat is the main reason you are shopping, ceramic film is the proven choice. The numbers by line are in Ceramic Tint: What It Is, How Much Heat It Blocks, and What It Costs.

Tint laws care about how much light reaches the driver through the glass while driving, not how the film works. Every state sets a minimum visible light transmission (VLT) for front side windows, many set one for the rear, and windshields are limited to a strip or a clear film. Check your state at Window tint laws by state.

That creates two problems for smart tint. First, standard PDLC is frosted when unpowered, which blocks a clear view, which front-window rules prohibit regardless of any meter reading, and hides of mirrors and traffic, so it must stay powered and clear whenever you drive. Second, even when clear the film adds a layer to factory glass, so the combined VLT has to be measured. Gauzy notes that side, rear and roof use is widely accepted while windshields face stricter rules.

The safe approach is to put smart film only on rear side windows and the back glass, where many states allow privacy-level darkness, and leave front windows with a legal conventional film. Tint percentage simulator shows what each legal shade looks like.

For most drivers, no. Ceramic tint costs $450 to $700 on a sedan, lasts the life of the car, rejects a published 48 to 59% of solar energy at 35%, and is legal at the right shade. A standard four-door switchable kit lists at roughly two and a half to four times the price of ceramic, and Flip Tint at five times or more, before labor; it adds wiring that can fail, and must sit clear on front windows whenever you drive.

It is worth it in narrow cases: a limo, van or SUV where rear passengers want privacy at the push of a button, a show car, or a buyer choosing a factory dimming roof on a new car. If that is you, insist on a written quote listing the film brand, the controller, the wiring path and the warranty, and ask what state the windows fail into. For everyone else, use Window Tint cost by vehicle for a local ceramic tint price, and Window Tint to compare studios by their public Google ratings, review counts and manufacturer certifications.