This car needs to be 20 percent cooler

A couple of years ago, we were debating the non-chromatic value of automotive colors, and this wisdom was proffered (not by me):

[I]t would be an interesting job for the Mythbusters to determine if white cars really do stay cooler than, say, red. (My gut feeling is “probably not, but the window tinting will help.”)

Well, there’s now actual research on the matter:

Researchers in Berkeley Lab’s Environmental Energy Technologies Division have published a new study that suggests cooler-colored cars could be up to 2 percent more fuel efficient than darker-colored ones. Their research shows that cooler colors like white and silver can reflect as much as 60 percent of the sun’s rays, while darker colors like black only reflect around 5 percent. This means that after sitting in the sun for an hour, a silver car’s roof is a full 45°F cooler than a black car’s roof, which, according to the researchers, would equate to a 9 to 11°F difference in cabin air temperature.

Nothing to sneer at. And here’s where they think they see the fuel savings:

If a cooler-colored car stays 9 to 11°F cooler inside on a hot, sunny day than a dark-colored car, it should require a smaller, more efficient air conditioning system to cool the cabin down to a comfortable temperature of 77°F within 30 minutes, which is an industry standard for vehicle air conditioning performance. The researchers then used a vehicle simulation tool to estimate the potential energy savings of using more reflective-colored paint to downsize air conditioners and found that switching from black to white or silver would increase fuel economy by 0.44 mpg, or 2.0 percent.

Then again, I have a white car with a “dark taupe” (something a bit darker than cheese mold) interior. I suspect that offsets some of the cool.





3 comments

  1. fillyjonk »

    3 November 2011 · 9:48 am

    Two reactions:

    1. If Henry Ford were reincarnated as an environmentalist, his tagline would be “a car in any color, as long as it’s white”

    2. To be 20% cooler, I think the car would have to have a rainbow-striped ragtop.

  2. Jeff Brokaw »

    3 November 2011 · 10:36 am

    An awful lot of guesstimating, wishing and hoping going on here.

    The researchers used a “vehicle simulation tool to estimate the potential energy savings” with downsized air conditioners that may or may not ever be available.

    All to save .44 mpg — maybe — for people who (a) live in hot climates and (b) buy white or silver cars instead of black.

    Well, guess what, Sherlock, very few people who live in hot climates buy black cars in the first place … because they are too damn hot.

    Good thing we’ve got Berkeley to sort out the obvious for us.

  3. CGHill »

    3 November 2011 · 10:53 am

    I don’t think I’d mind a rainbow-striped ragtop, despite my general preference for inconspicuousness.

    The problem with A/C generally is that right about the time the patent on a refrigerant runs out, somehow it’s discovered to have Deleterious Environmental Effects, and the regulations must be cranked up to, oh, let’s call it R-12.

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