AskPablo: Black Google

blackle.jpgThis week’s question comes from Julia. She asks “is it really true that a black Google page would save energy?” She is, of course, referring to a very popular article written by Mark Ontkush back in January. He claims that turning the Google page black would save 3000 MWh per year! As a result, Blackle was created. While it may be true that a CRT monitor uses 15 watts less with the black screen Mark does admit that only 25% of the world’s monitors are CRT. What about the rest of us, with shiny new LCD monitors?

According to Nielsen/NetRatings (“Researchers take time out to measure online audience,” Financial Times, July 16, 2007, p. 15) Google users spent 2,557,000,000 minutes on Google websites in May of 2007 (746M for Yahoo, 7,535M for MySpace, and 2,117 for Youtube). That’s 426,616,666 hours, or roughly 4,865 years! Over the course of one year that would amount to 511,400,000 hours of Google website use.
For the 25% of CRT users there is a savings of 15 watts. This does amount to 1,917,750 kWh saved (511,400,000 hours x 25% x .015 kW). For LCD screens it’s a different story. While CRT monitors function like a light bulb, getting dimmer and brighter, and therefore using more and less electricity depending on screen brightness, LCD screens are a back-lit display where a liquid crystal display selectively blocks out certain wavelengths of light. What this means is that, when I hook up my Kill-A-Watt meter to my screen I get a reading of 16 watts when it is on the regular page. Surprisingly, I actually get a reading of 17 watts when I switch over to the page! So, with a black screen a LCD monitor actually uses 1 watt more. If 75% of monitors are LCD this amounts to 383,550 kWh (511,400,000 x 75% x 0.001).
So, while the net savings are 1 534,200 kWh (1,917,750 – 383,550) it probably does not make sense for LCD monitor users to switch to the black screened Google. This also means that screen-savers don’t actually save you any energy either. In fact, running the video card that powers the screensaver may use even more electricity. The best setting, therefore, is for your monitor to turn off or your computer to hibernate.
I would also like to point out that the black Google does not save any energy in the server hardware that runs the website, or in the desktop/laptop computer that you view it with, which is where most of the energy gets consumed.
So, there’s your answer Julia…
Pablo Päster, MBA
Sustainability Engineer