Are Sunshades Effective At Lowering Temps In Your Parked Car? - Jalopnik
Sergio Grisaldi/Shutterstock It seems self-evident that a sunshade inside a car's windshield would be pretty effective, for the same reason that blinds or c...
Sergio Grisaldi/Shutterstock
It seems self-evident that a sunshade inside a car's windshield would be pretty effective, for the same reason that blinds or curtains in your home prevent the interior from getting too hot. Even the ancients understood cooling, and according to Smithsonian Magazine, the Romans used wooden shutters to keep their palaces cool. But what about your chariot? What's the right way to prevent the inside of your beloved ride from roasting?
Way back in 1988, scientists at the University of Central Florida's Solar Energy Center parked a pair of identical Toyota Tercels (not exactly chariots) at Cape Canaveral to measure the effects of using simple cardboard behind the windshield and foil reflector sunshades. They found that the interior of a car parked in the sun can reach 150 degrees Fahrenheit and dashboard temperatures can approach 200 degrees F. But applying a piece of cardboard behind the car's windshield can reduce interior temperatures by an average of 15 degrees F and reduce dashboard temperatures by a very substantial 40 degrees F. Using foil-backed shades as blockers cuts temperature even further, by three to five more degrees for the interior temperature and steering wheel. Dashboard temperatures went down a further 6 to 11 degrees. Bottom line, sunshades help. But other methods prove even better.
A sunshade on the outside of your windshield is more effective — and so is a car cover
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Malaysia is a pretty hot place, so it makes sense that they'd spend time studying sunshades there. A paper presented at the 2012 International Conference on Mechanical, Automobile and Robotics Engineering in Penang argued that using a basic nylon shade in the front windshield — not too different from what one of our own journalists advocates as a cheap hack for a window shade — could significantly reduce dashboard temperatures. In their tests, using a nylon sunshade dropped the scorching 189.5 degrees F dashboard temperature by 32.6 degrees F.
If you're going to park in the sun for a while, however, there are better solutions, at least according to Germany's Allgemeiner Deutscher Automobil-Club (ADAC) (General German Automobile Club), Europe's largest automotive club, much like AAA. ADAC's 2026 study of various passive cooling methods found that a partial exterior car cover reduced the internal temperature from 127 degrees F to 109.4 degrees F. That was the most effective method. Putting a reflective sunshield outside the car's windshield was much more effective than one inside, cutting the temperature from 127 degrees F to 113 degrees F and essentially preventing as much heat as possible from penetrating the windshield.
Shoving that shield inside the windshield glass allowed the car to heat up much more, to 120 degrees F. That temperature rose to 122 degrees F with a simple white cloth on the interior, which did very little to prevent cabin temperature from rising.
Park in the shade and save gas
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The Department of Energy says that using your car's air conditioning on maximum can cut your car's fuel economy by as much as 25% — so try this science trick instead, right when you clamber aboard your burning-hot ride. And heed the Oak Ridge National Laboratory, and park in the shade in the first place to keep the temperature in your car lower and avoid having to use your AC on full blast.
Other factors that determine how hot your car gets might already be, uh, baked in. ADAC found that the surface temperature of a black car parked under an unrelenting midday sun reached 149 degrees F, while a white car was, relatively speaking, a cooler 111 degrees F. That translated to the black car hitting 127 degrees F inside, versus 118 degrees F for the white car. By the way, regarding fuel savings, car color matters here, too. 2011 research by scientists at the Lawrence Berkley National Laboratory found that cooling a heated silver car to a comfortable 77 degrees via the A/C required 13% less energy than an identical black car. And FYI, dark-colored cars can even raise urban air temperatures where they're parked.
Plus, all parked, non-running cars are a danger to kids. Definitely never leave a child in a parked car, even on a mild day. Consumer Reports showed that even if it's a relatively temperate 61 degrees, the interior of a car can reach 105 degrees F within an hour. That can lead to deadly heatstroke, and Consumer Reports says over half of all child hot car deaths have been caused this way. Don't let that happen; use a sunshade, ideally on the outside.