Aug 1, 2007

Saving Electricity With Color

Can a web page's background color save electricity?

I have some input with regards to the claim that the color black uses less electricity. This claim is TRUE for CRT monitors (the big old clunky ones) but is FALSE for LCD monitors (the thin kind that come with laptops and newer desktops).

BLACK USES THE SAME OR MORE ELECTRICITY ON LCD MONITORS, NOT LESS. This is backed up on the FAQ from the original site that posted the power savings calculations [1]. This is because of the way an LCD works which is approximately opposite of a CRT -- an LCD (think laptop or digital watch) has a backlight that is on all the time and electricity is used to change pixels to COVER the white backlight [2]. The more, darker pixels you show, the more electricity you use to cover them. A CRT (think desktop computer or old tv) works in the opposite fashion, showing black by default and shooting electrons towards a fluorescent screen which then lights up [3].

My own trials viewing and and measuring immediate watts via my trusty Kill-A-Watt(tm) electricity meter[4]:

Google Blackle Difference Machine
CRT 108w 79w -29w 20" Sony Trinitron
LCD 21w 22w +1w Dell Latitude D820 laptop

While blackle saved (significant) electricity on my desktop, it used MORE electricity on my laptop, not less. Also note that the CRT viewing blackle still uses almost 4x the electricity than the LCD viewing google.

I'm glad to see that the folks at the HoS are serious about saving electricity; if you're still using a CRT monitor then by all means, use as many black backgrounds as possible. However, if you use an LCD monitor (the flat kind) you should stick with regular old with a light background.

Some other simple things you can do to conserve electricity while using your computer:

  • Switch from a CRT monitor to an LCD. LCDs use a small fraction of the electricity of a CRT. Even getting an electricity-guzzling CRT for free can be more expensive over its lifetime than paying a few hundred dollars for an energy-efficient LCD screen.
  • Use a screensaver! Use a "blank screen" screensaver instead of an animated one. Screensavers are meant to save the screen's pixels from getting "burned in", not electricity [5].
    • Use a white background on an LCD screensaver
    • Use a black background on a CRT screensaver
  • Reduce the brightness of your monitor
  • Use the Energystar "Power Options" or other "sleep mode" on your laptop to make it hibernate while inactive
  • Turn your computer off when you're not using it


  1. Facts and Fallacies on Black Google
  2. Liquid crystal display
  3. Cathode ray tube
  4. Kill-A-Watt Electric Usage Monitor
  5. What Are Screen Savers For?
I challenge you NOT to take what I say at face value, but test it for yourself. If anyone wants to borrow my Kill-A-Watt electricity monitor (it's small, harmless and very easy to use) please let me know. Thanks for your time.


Ryan Flynn is a programmer and problem solver.