Reference Links:
http://ecoiron.blogspot.com/2007/01/black-google-would-save-3000-megawatts.html
http://savingenergy.wordpress.com/2006/11/21/saving-energy-one-monitor-at-a-time/Black Google Would Save 750 Megawatt-hours a Year
As noted, an all white web page uses about 74 watts to display, while an all black page uses only 59 watts. I thought I would do a little math and see what could be saved by moving a high volume site to the black format.Take at look at Google, who gets about 200 million queries a day. Let's assume each query is displayed for about 10 seconds; that means Google is running for about 550,000 hours every day on some desktop. Assuming that users run Google in full screen mode, the shift to a black background will save a total of 15 (74-59) watts. That turns into a global savings of 8.3 Megawatt-hours per day, or about 3000 Megawatt-hours a year. Now take into account that about 25 percent of the monitors in the world are CRTs, and at 10 cents a kilowatt-hour, that's $75,000, a goodly amount of energy and dollars for changing a few color codes.
Saving Energy - One Monitor at a Time
Several times I had observed that my laptop battery lasts a lot longer if I turn down the brightness of the screen. That just seems such a common sense thing to do. But I never took power consumption of monitor that seriously till one day I almost burned my hands while trying to move the big bulky 19 inch CRT monitor. The back side of the monitor was really hot.
Boy, how much power does this one consume? A quick look at the manual and turns out that my old big bulky 19” monitor was consuming a whopping 120 Watts. It’s like having a big bright bulb burning right in your face. That figure was big enough for me to switch off my monitor while not working. But still I wondered, what is the exact relation between what is being showed on screen and how much power is being consumed by the monitor.
A really good EBay deal on P4400 KillAWatt by P3 International convinced me that God wants me to buy a power meter and investigate this in detail. For anyone interested in “watching your power”, this is a handy thing for about $30.
I ventured onto this study. I checked monitor power consumption for CRT (Cathode Ray Tube aka big, bulky, heavy, TV shaped, ugly, dinosaurs), as well as LCD monitors (Liquid Crystal Display aka thin , flat, light, cool cuties) . Since 17” monitors are the most common, I chose Compaq S710 in my office (which is CRT 17”) and Hundai Imagequest L70N, which is LCD 17” monitor for study and comparison.
I checked following things
- CRT monitor consumption vis-à-vis LCD monitor consumption
- Brightness settings varied 0, 50, 100
- Contrast settings varied 0, 50,100
- Screen background changed black, gray, white
- Soft power off (off using power settings of computer) and hard power off (off using switch) consumptions.
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Comments:
1.
You'll find a lot of pages out there that claim "many studies have shown ... that dark text on light background is easier to read". I have always suspected that this is due to the historical accident that physical writing works best with dark ink on light paper-ish stuff. I wonder how many of "those studies" studied populations that grew up unbiased -- i.e., grew up and learned to read without the historical accident of paper-based (dark on light) reading.
2.
Only CRT displays use more energy to display brighter things. For everything else, it is completely false that a black display uses less energy than a white page. The backlight on an LCD is on for the entire LCD regardless of what is being shown. The black pixels are only black because the LCD blocks out light. Same with projectors, etc. You're article is thoughtful, but invalid.
3.
This may be true for CRT monitors. But, LCD monitors use significantly less energy and I don't think their wattage varies much depending on the colors displayed.
4.
Something to consider: If Google were to change the color scheme to all black, Google would loose AT LEAST 50% of its user base (dare I say 80%?). The "tech Elite" could find work arounds such as using Firefox extensions (Stylish or Greasemonkey), but the vast majority would just switch REGARDLESS of the fact that functionality remained the same.
All the money Google would be saving people (assuming the accuracy of this article) would be guzzled in the end by Google's competition: Yahoo And Microsoft have lots of white on their search pages.
Fact is, this entire idea of Google saving energy by switching to "black" would lose GOOGLE money, and not be much better energy wise at then end. Not only will it never happened, but even if it did no good would come of it (for anyone).
5.
Very good point, Pjotr. In fact, every time people come up with these statistics about minute differences multiplied by millions, they forget that on such a scale there are gazillions of other minute differences on the same scale you can't possibly take into account. One of them is indeed the fact that people would probably spend slightly more time looking at the displayed page. But there's no telling how the mood-change of a black page influences the rest of the user's browsing session. Again a normally neglectable difference, but not when multiplied by millions.
Another much more concrete influence though, and this is forgotten almost every time "energy waste" is calculated, is that this extra power consumed by the monitor, is eventually transformed into heat which, if you have a thermostat in the same room, is deducted from the energy use of your heater. You won't notice this on either your gas bill or electricity bill of course because the differences for one person are too small to notice. The point is, that even multiplied by millions, these and other factors will continue to cancel each other out in a way you can't really predict.
All this may seem nitpicking, but the real point is that you can't just take a single neglectable difference, multiply it on a huge scale and think that you know the total effect. The world simply isn't that simple.
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The Summary of the findings is below
· Sensitivity to various settings is as follows
| Power Consumption Parameter | CRT Monitor | LCD Monitor |
| Avg. consumption | 76 W | 20 W |
| Screen color sensitivity | Extremely sensitive. Consumes lot more power (43% more) when displaying white on screen. | Completely insensitive. Consumes same power for all colors on screen. |
| Brightness setting sensitivity | Moderately sensitive. Consumes more power at higher brightness. | Sensitive. Consumes higher power for higher brightness |
| Contrast setting sensitivity | Less sensitive. (Almost insensitive when brightness setting is low.) | Completely insensitive. Consumes same power for all contrast |
| Consumption when turned off from computer power settings | 2W | 0 W |
