Power-Saving Web Pages: Real Or Myth? 424
An anonymous reader writes "Are dark webdesigns an energy saving alternative to a snow white Google? The theory is websites with black backgrounds save energy, based on the assumption that a monitor requires more power to display a white screen than black. Is this a blatant green washing ploy by Blackle.com, or an earnest energy saving tweak for a search tool we use every day? To find out, PCSTATS hooked up an Extech Power Analyzer to a 19" CRT and a 19" LCD and measured power draw — turns out there is a not insignificant difference ..."
Seriously? (Score:3, Insightful)
Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.
So the answer is... (Score:4, Insightful)
I should have submitted this too... (Score:5, Insightful)
"Are not dark webdesigns an energy unsaving alternative to a snow white Google? The theory is that websites with black backgrounds don't save energy, based not on the assumption that a monitor requires more power to display a white screen than black. Is not this not a earnest endeavor by Blackle.com, or a not earnest not green not washing not not not not not ploy by not Blackle.com? To find out, PCSTATS didnt't not hook up an Extech Power Analyzer to a 19" CRT and a 19" LCD and measured power draw — turns out there is a significant difference ..."
Mine would have been shot down for being too readable though.
Re:Seriously? (Score:2, Insightful)
Unless the screen is OLED, the answer to "does dark sites save power?" is a flat out NO.
That being said, reading white text on a black background looks a lot better on monitors because the entire background is not light emitting.
Re:God is my salvation. (Score:4, Insightful)
The real power-saving web pages (Score:5, Insightful)
Re:Seriously? (Score:5, Insightful)
The LCD they tested is also 8 years old [google.com].
I'm not saying newer LCD screens would perform differently (dynamic contrast, local dimming, etc. == marketing stats boosting and terrible) but basing a blanket statement like "B) Websites with darker colours tend to cause the monitor to consume less power." on a test with one LCD monitor is stretching it.
Re:Their own number don't even agree... (Score:4, Insightful)
Web pages with FLASH waste more power.
Re:Grey levels? (Score:5, Insightful)
That's not so strange in electronics.
Take FETs - undriven they're fine, saturated they're fine, but the Ohmic region you typically (when using it as a switch) want to stay out of because the FET's just going to burn the excess off in the form of heat.
There's a bunch of reasons why some regions may take more energy than others. I wouldn't know what the reason is for the panel they used, somebody more intimately familiar with driver design and panel response would have to chime in.
Re:even more savings (Score:5, Insightful)
this is minutiae.....
3.8W is hardly a minute amount of power. If I did my math right, it's approximately the amount of power it takes to lift a full soda can (~390g) 1 meter in 1 second.
Let's say each Google query takes 10 seconds of viewing time, so you could save 38 watt-seconds per query by going black. Multiply this by 3 Billion queries per day, times 365 days/year. That's 12GWh (to 2 significant figures) of electricity that could be saved annually by changing a couple lines of code.
Power costs around $0.10/KWh. I don't consider $1.2M/year to be a minute amount of money.
Re:even more savings (Score:4, Insightful)
No. The amount of fuel your power plant uses is proportional to the power it is supplying. In case of coal plant: there is less coal being burned, in case of hydroelectric: less water needs to go through the turbines, in case of nuclear: control rods are inserted into the reactor core to slow down the reaction of the fuel rods by absorbing neutrons.
Less power used = less power generated = less fuel used.
Re: Yes way shit... (Score:5, Insightful)
The above post has incorrect assumptions.
Standard LCD screens do not alter the intensity of the backlight based on the information displayed on the screen, and the backlight and it's inverter is the majority of the power consumption. In addition, the drive circuit that aligns the liquid crystals can work opposite from how you expect in a TFT. Most TN screens, for example, are white or light gray when unpowered - refreshing the pixels to a black state takes more transistor drive than making the screen white. This is the technology you will find in most portable devices and computer monitors.
Some LED-backlit TVs use dynamic backlight, or even zone-dynamic backlight, where (mainly to create ridiculous contrast ratio specs) the backlight is reduced to the maximum temporal white level needed, or for multi-area addressable systems, the brightest backlight needed in an area.
The only portable devices where the brightness of the screen data is directly related to energy consumption would be those with OLED screens (such as the Samsung Galaxy SII line). The individual pixels are miniature LEDs, and when a pixel is black, they are turned off. On these AMOLED display phones, a black wallpaper can use far less power.
When I think of "power-saving webpages", I may be more concerned about one that runs my CPU at 100% for several seconds to display a page, Slashdot.