James5

A friend just sent me the link to Blackle, an “energy saving” version of Google. The theory is that using an all white background takes more energy to display then an all black background, so Blackle is Google gone black. Blackle’s stats say that an all white display uses 74 watts whereas an all black display uses only 59 watts. That’s almost a 31% saving of energy!

However, as always, the devil is in the details. First of all, the above calculations are only relevant for CRT monitors – which currently account for 25% of screens worldwide (and dropping). For those thin LCD monitors there is either no saving or it may even use more energy to display black pixels! So if you use an LCD, don’t bother with Blackle.

Secondly, grey text on a black background is probably a bit worse for your eyes then black on white. Studies have shown that it’s harder to read and it can even cause some people pain. For vision-impaired people it’s no good either.

Thirdly, and perhaps most importantly, the saving isn’t really that large for CRTs anyway. The Blackle screen is usually only displayed for a few minutes per session, once a user finds the page their looking for they leave the blackness. Blackle’s own stats estimate that the total saving, of all their users not per user, at only 1/7 the power of 1 utility scale wind turbine. At last count they had saved 4.4 kWh, about 1/8 the daily consumption of an average US household. While I know that every bit counts, the amounts saved here are very small, especially when you consider that LCD users are probably tipping those stats a bit.

Turn off your monitor and save 3kg of CO2 per year!A better way to save energy with your monitor is to simply turn it off. Rather then using a screensaver, you can set your options to automatically turn off your monitor when not in use – but it’s better to actually use the monitors off switch. An average CRT uses about 20w of power when idle. If your monitor is off for just 15 minutes more per day, you could save 7.3kWh per year or about 3kg of CO2 per year! That’s almost double the entire saving of Blackle to the present! 15 minutes a day should be very easy to achieve. Bathroom breaks, lunch, meetings, if we turned it off whenever we were away from the computer it would quickly add up.

So if you want to save energy with your computer, there are probably better ways to do it then Blackle. Some people are arguing that Blackle is also about “awareness raising”, that Blackle reminds you to save energy if you set it as your homepage. But I’m not convinced that the positives outweigh the negatives in this case. Just use a post-it note on your screen reminding you to turn it off when you go the bathroom and you’ll be making a much bigger difference.

Even though I could think of a cheesy ad campaign to convince people to “go black” (something like “once you go back you never go back”…), I think in this case “staying white, is probably alright”.

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