Black Pixels Cost Less?

I was recently introduced to a Google search wrapper called  It's sole claim to fame is that it displays a Google-like search page, but with a background color of black.  Why? claims that black pixels require less energy to display than white pixels, so if everyone who uses Google were to see a black screen instead of white, the world would collectively save upwards of "750 megawatt-hours per year" of electricity.

Those are grand claims.  While the sentiment to save energy and reduce environmental impact is well placed, I was skeptical.

So, I dug out my only CRT monitor from the closet and hooked it up to my Kill-A-Watt power meter and my laptop's external video connector.  For a white screen, I used an Outlook message editor window, maximized.  For a black screen, I used a cmd prompt window, maximized.

Nokia 447x 21 inch CRT:  Black screen:  75 watts.   White screen:  101 watts.

On the surface, these results appear to support the claims and pie-in-the-sky global estimates. 

However, there's a catch.

Look at the results for an LCD monitor: 

Samsung 21 inch LCD model 204B:  Black screen:  36 watts.   White screen:  36 watts.

LCD screens use fluorescent (or recently, LED) backlights to illuminate the screen.  The backlights consume the same amount of power regardless of whether the LCD crystals are showing black pixels or white pixels.  If anything, LCDs have to work harder to show black pixels because they are flooded with white light.  In a CRT, black is the default state and the CRT has to work to make a white pixel.

LCD screens have been outselling CRTs for many years now.  Laptops surpassed desktop sales years ago.  I don't know if there are already more LCD's in the field than CRTs, but it's clearly the case that LCDs are growing while CRTs are in decline.  Odds are, you're reading this text on an LCD screen.

While it's true that a black pixels consumes less power than a white pixels on a CRT screen, pixel color has no effect on LCD power consumption.  Given that LCDs are a large and growing (and possibly majority) portion of the global monitor population, the power savings claimed by is a case of diminishing returns.

Comments (6)
  1. Rosyna says:

    these claims may become true again in the future. There are some LED backlit screens by samsung (I think) that have LED backlights in a grid like pattern. It can turn off the backlight (or dim them) on sections on the screen that have darker colors, thereby saving some power and producing truer blacks.

  2. I have always been a fan of dark UI-backgrounds, especially for code-editors. I used dark schemes like

  3. MSDN Archive says:

    Hey, whatdaya know!  Google just blogged about this, too:

  4. bcthanks says:

    Your power measurements for the Samsung 204B monitor are way off… I own one and it averages 35W regardless of the image displayed. That is consistent with a 21" NEC MultiSync LCD panel.

    LCD monitors are getting brighter and brighter every year… I turned down the brightness of my Samsung panel because the factory setting hurts my eyes! Out of the box this monitor draws about 45 W.

    I agree there’s no power to be saved with a black background on a LCD monitor, but your incorrect measurements isn’t helping to convince people to ditch their CRT. Before I got my own power meter, I did not know that replacing a 21" CRT with the Samsung saves 90W… had I known that, I would’ve switched years ago.

    Over on Raymond Chen’s blog, somebody said "I bet on that test he forgot to switch his Kill-A-Watt meter from the default Volts mode to Watts."

  5. MSDN Archive says:

    Woops – you’re right.  The LCD watts were over stated, but same result.  Figures corrected in the article.

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