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Power-Saving Web Pages: Real Or Myth? 424

Posted by timothy
from the raise-your-hand-if-you-think-real dept.
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 ..."
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Power-Saving Web Pages: Real Or Myth?

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  • Seriously? (Score:3, Insightful)

    by Cinder6 (894572) on Thursday April 19, 2012 @04:32PM (#39738311)

    Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.

    • Re: (Score:2, Informative)

      by Anonymous Coward
    • Re: (Score:2, Interesting)

      by idontgno (624372)

      I bet "Anonymous Reader", our submitter, who probably shills for "blackle.com", "believes" it.

      I can't decide if this story is an intentional slashvertisement or an astroturf.

      "Blackle.com"? Really? It's only slightly clever to raise the possibility that they're trying to greenwash the issue of "website-specific power consumption", especially since TFS very conveniently refutes that. ("not insignficant?" Sheesh.)

      • Re: (Score:2, Insightful)

        by Shikaku (1129753)

        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.

        • by Ferzerp (83619)

          You realize that CRTs use less power with darker images for basically the same exact reason?

        • by Yetihehe (971185)

          I like reading black on white. With white text on black bg I have afterimages of text lines and this is sometimes rather confusing when trying to read text with another line spacing.

        • Re:Seriously? (Score:5, Informative)

          by amicusNYCL (1538833) on Thursday April 19, 2012 @04:51PM (#39738623)

          Unless the screen is OLED, the answer to "does dark sites save power?" is a flat out NO.

          How you do figure, where's your data? Their data clearly shows that a CRT displaying all white uses 85W, and the same monitor displaying all black uses 63W, which sounds to me like it's using 25% less power to display the black screen. For an LCD the difference is only about 10%. The grayscale comparisons clearly show a relationship between darkness and power draw.

      • by AmiMoJo (196126)

        Have you actually visited blackle.com? It is just a Google search box with a black background. No advertising, no agenda other than someone who seems to have a genuine point.

        Even LCDs seem to benefit to the tune of 10% energy savings. 10% over thousands or millions of computers is a lot.

        It would be interesting to see stats from more monitors, and also from mobile phones with OLED screens. I have a feeling that the Samsung monitor they tested is one of the smarter ones that reduces blacklight levels when the

    • Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.

      No, the big power draw is from CRT displays.

      Both of them. They'll die someday and things will be nice and green again....

      • by Anonymous Coward on Thursday April 19, 2012 @05:20PM (#39739051)

        No, the big power draw is from CRT displays.
        Both of them. They'll die someday and things will be nice and green again....

        Back in my day the CRTs were green... or sometimes amber.

    • Re:Seriously? (Score:5, Informative)

      by QuasiSteve (2042606) on Thursday April 19, 2012 @04:39PM (#39738449)

      Seriously?
      Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.

      Yes, anyone here actually believed this. I guess in your hurry to post, you misread the double-negative in the summary...

      turns out there is a not insignificant difference

      ...that actually indicates that there is at least a measurable difference.

      Note that their measurements apply specifically to the two models they tested, a CRT and a particular LCD.
      If 'white' means you have to drive the LCD, then white takes more energy. If 'black' means you have to drive the LCD, then black takes more energy. Most LCD drivers are standardized, though - and given the prevalence of lighter content, it may be worth it to the industry (even if only so they can use it in marketing) to switch the defaults.

    • Re:Seriously? (Score:4, Informative)

      by Anonymous Coward on Thursday April 19, 2012 @04:39PM (#39738451)

      The link was to pcstats.com, which actually tested the claim. There was a ~25% difference between all-white and all-black screens on their test CRT, and a ~12% difference between the two on their test LCD.

      They tested a lot more sites than just Google and Blackle.

      • by Ihmhi (1206036)

        I am fine with this data being spread and loads of websites switching to white text on a black background. I think it looks cooler, and moreover it is way, way easier to read. Sometimes the white background of a screen just assaults the eyes.

    • Re:Seriously? (Score:4, Informative)

      by betterunixthanunix (980855) on Thursday April 19, 2012 @04:41PM (#39738483)
      Some monitors will reduce the brightness of the blacklight when the screen displays a very dark image.
    • by Xeranar (2029624)

      I've never understood this argument they had about black bakgrounds. The backlight is always on and hence why we should all be using LED or the newly available translucent monitors that use ambient light. I think the myth is due to our perception of light & dark. We fail to understand black on a monitor is a lack of color and an absorption of all light but the backlight as stated operates independently of the display's image.

    • No, the power draw is from the heaters and the deflection circuitry, but each gun that is turned on at full intensity also adds to the total (that's why full screen yellow uses more power than full screen red or green).

    • Re:Seriously? (Score:5, Insightful)

      by dinfinity (2300094) on Thursday April 19, 2012 @04:51PM (#39738635)

      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.

      • by fbjon (692006)
        Wouldn't a newer monitor with smarter backlight usage show a greater difference in power draw? It seems they've tested the worst case and still got a 10% difference.
    • by Joce640k (829181)

      Did anyone here actually believe this?

      I dunno...but I DO know my eyes are funny for a few minutes after I try to read any amount of white-on-black text - it causes massive afterimage.

      (Yes, I have the "nostyle" Firefox plugin to deal with these websites)

    • by tlhIngan (30335)

      Did anyone here actually believe this? The big power draw is from the backlight, which is still running even with black pixels.

      Actually, it can. Modern LCD displays are crap at this - they employ crap like "local dimming" and "global dimming" to get their stupid contrast ratios. As a side effect, displaying a dark screen does save power because the backlight dims to make the black blacker.

      Conversly, displaying a white screen cranks up the backlight to make it brighter, which takes more power.

      Since contrast

      • by tlhIngan (30335)

        Other thing... white on black is hard on the eyes because of "black creep". If you're a typesetter, you know this - if you have light text on dark background, you have to increase the siez of the text in order to keep its apparent size the same. Also, thin fonts sink, so you may have to apply bolding to "fatten" them so they're still legible when the black background slims them down.

        • Re: (Score:3, Interesting)

          by Anonymous Coward
          I know way too much about printing, but I can't find anything about this "black creep" online, but it sounds exactly like dot gain [wikipedia.org]. Well, except for you thinking it's in people's eyes.
    • Re:Seriously? (Score:4, Informative)

      by sunderland56 (621843) on Thursday April 19, 2012 @05:40PM (#39739317)
      The report is internally inconsistent.
      • First they state figures for an all-white screen in their "Black and White" test: 85.1W (CRT), 38.4W (LCD).
      • Then later they test an all-white screen in their "Greyscales" test: 84.9W (CRT), 40.0W (LCD).

      So they show a 1.6 watt difference (LCD) on the same image, where their stated difference between google and blackie is 3.8 watts.

      • by ceoyoyo (59147)

        That's not inconsistent. It's called error, or noise. Never trust a value with no error bars.

  • Can I do an image search or a news search right from the home page? I am not sure if Google Custom Search supports these features beyond a simple web search.
  • by Anonymous Coward on Thursday April 19, 2012 @04:33PM (#39738337)

    "turns out there is a not insignificant difference "

    Double negatives are not not bad.

    • Re: (Score:3, Informative)

      by Anonymous Coward

      In this case, the double negative has a valid use. By saying "not insignificant" it leaves all other possibilities except for insignificant. This doesn't necessarily mean that the difference is significant, just that it isn't insignificant. If they said there is a "significant difference" then they have left only one option - that the difference is significant, and that statement carries more weight.

  • by zaibazu (976612) on Thursday April 19, 2012 @04:34PM (#39738349)
    I am interested in black background websites because they look prettier on OLED displays (Old Samsung Galaxy here as a reserve phone) . Readability should be driving the decision on the colours, not some % power saving.
  • by fropenn (1116699) on Thursday April 19, 2012 @04:35PM (#39738373)
    buy an LCD (or LED) screen. That will save much more electricity than changing the colors you use on it. I can never figure out why so many energy saving tips focus on such small things (e.g., turn off the water when you brush your teeth) but ignore the big issues (like my neighbors who water all afternoon in 100 degree heat and have a stream of water running directly into the sewer).
    • by idontgno (624372)

      The time-honored metaphor for this is "carefully arranging the deck chairs on the Titanic as it sinks." We can fiddle trivial stuff and satisfy ourselves we're "DOING SOMETHING FOR <great cause>" while not actually changing the costly, momentous, or personally-significant things.

      See also Matthew 7:3-5 if you're not opposed to Biblical proverbs.

    • by TheCarp (96830)

      Well if you already did that....

      Frankly, I wonder why they didn't test the one thing I do as soon as I get a new LCD, which is actually recomended by several sites out there.... turn the brightness down to under 20%, sometimes, I go all the way to "0" (interesting that 0 brightness is not a black screen).

      As an N=1 test, after realising that I couldn't easily tell the difference after a minute or two, was to take one of the most observant and territorial about her PC people I know, and changed the brightness

  • OLED's (Score:4, Informative)

    by imgod2u (812837) on Thursday April 19, 2012 @04:36PM (#39738387) Homepage

    The idea is valid for all of the smartphones running OLED displays. OLED's take no power (or very little) to display a black pixel. It takes full power to display white.

  • Power is more of a concern on mobile devices and mostly dark/black displays will allow AMOLEDs to turn off some pixels to save power and extend battery life.

  • by dyingtolive (1393037) <brad.arnett@NOspam.notforhire.org> on Thursday April 19, 2012 @04:38PM (#39738425)
    Except I would have said

    "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.

  • by cpu6502 (1960974) on Thursday April 19, 2012 @04:44PM (#39738527)

    Maybe PCstats should apply their own power-saving strategies to themselves (less CPU-intensive flash crap).

    Anyway it appears only the CRT has a significant savings with White google versus Black blackle.com. LCDs gain almost nothing.

  • I'm not really double checking my #'s here....

    1 billion queries per day in 2011 (quick online search)... lets say that 1 user makes 100 queries/day (so 10 million users) and each query takes about 10 seconds to complete. 100 million seconds burning 4 watts yields 400 megawatts per day. If we average that out per hour, then we're burning 16 megawatts per hour 24/7. Each day, enough to power 8-16 households (1000-2000kwh) for a month... so over a month: 240-480 households with pretty wasteful practices.

    SO,

  • by crazyjj (2598719) * on Thursday April 19, 2012 @04:44PM (#39738537)

    Yay! My Black Sabbath fan site is one of the most environmentally-friendly sites on the internet!!

  • I've been running MessageBase [messagebase.net] with a black background because of this exact reason since the late 1990s. Everyone told me it was a stupid idea and the power savings were negligable.

    Think of all the power I've saved people! I've done my part.

    • by Hatta (162192)

      It's not just good for power. It's hard to stare at a white backlit source for a long time. Muted colors on a black background are the easiest on the eyes.

  • In the "Black & White" table they list white at 38.4 W, then in the "Greyscales" table list 0% grey (white) at 40.0W and 60% grey at 38.5W -- all for the same 19" LCD Samsung 192MP monitor showing a full-screen solid color. For fluorescent back-lights, I can't imagine the power usage to be that different for just toggling the LCD cells, but can for an LED back-light, where there are grids of LEDs that may be powered down/off for a more true "black".
  • by Shagg (99693) on Thursday April 19, 2012 @04:47PM (#39738585)

    Anyone else notice that (further down in the article) they measured 6 different levels of grey between 'white' and 'black', and 4 of the levels of grey actually measured MORE of a power draw than pure white on the LCD monitor?

    • by Hentes (2461350)

      Shadowing the backlight consumes some power in LCDs, except if the part is dark enough so they can dim the light in that sector.

    • Re:Grey levels? (Score:5, Insightful)

      by QuasiSteve (2042606) on Thursday April 19, 2012 @05:06PM (#39738853)

      4 of the levels of grey actually measured MORE of a power draw than pure white on the LCD monitor?

      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.

  • by ortholattice (175065) on Thursday April 19, 2012 @04:50PM (#39738617)
    The real power-saving web pages are simple and clean ones that that use the least CPU time to load, without bloated Web 2.0 javascript mashups of dozens of irrelevant sites and web bugs that keep track of you. TFA doesn't seem to mention that.
  • What about the CPU? (Score:5, Interesting)

    by queazocotal (915608) on Thursday April 19, 2012 @04:53PM (#39738671)

    Firstly, I'm extremely skeptical of one of the conclusions - 'flash will make a CRT monitor use more power' - which I just don't believe - it will use an amount of power dependent on the average screen brightness - which may be an increase over black.
    LCDs are different - the panel does actually take some energy to change state, and the lag compensation circuitry will use more in motion.

    Secondly - a huge part has been missed out of this.
    Power consumption of the computer.

    Flash, or javascript, even in the background, can considerably increase power.
    For example, I just closed all of the flash/animated things in the background on other tabs in firefox, and the CPU usage is now bouncing around 2%, with the computer using 17W.
    If I start up a new tab with some flash, and gif animations, it goes up to 25W. (+8W)
    Even switching away from the tab only takes it to 23W or so. (+5W)

    It would be interesting to work out the total electricity wasted by common flash ads.

  • by DontLickJesus (1141027) on Thursday April 19, 2012 @04:54PM (#39738673) Homepage Journal
    With recent changes in browser specs to allow for monitoring of battery levels, I've really taken an interest in this debate. Consider a web based application which has a critical function to complete, yet the battery is dying. Said application could switch it's color scheme to something darker in order to conserve battery and allow that function to complete before draining the battery. It's an edge case scenario, but mobile apps offering a "low power" mode would be a great way to promote usage.
  • by Alain Williams (2972) <addw@phcomp.co.uk> on Thursday April 19, 2012 @04:59PM (#39738765) Homepage

    It would have been interesting to include the whole computer in the power measurement. How much more electricity is drawn by a javascript infested site than one that is just static HTML and images ? How much more is drawn if there are 100 components to build the page instead of 20 (don't forget to include the consumption of your broadband modem, etc, ...) ? How much more electricity does flash use ? How much more through heavy use of AJAX ?

    The biggest difference that they showed was that the use of a glass monitor was about double that of a LCD. With an LCD the CPU/... consumption would be a bigger fraction of the whole thing.

  • I can't imagine with current LCD's that this would even matter.
  • A 11% difference between full white and full back is more or less insignificant to me.

  • Some phones have OLED screens that consume less power when displaying dark colors.

    Another reason is nighttime usability on a smartphone. Too much light is blinding after your pupils have dilated to accommodate the dark.

  • Meh... What I'd want to know is, by how much do you decrease a site's power consumption when you strip out:

    1. Needlessly complex HTML. (sidebars, header, footer, occasionally content...)
    2. Scripts, CSS files and cookies from all over the place (I'm looking at you, ads)

    Or to put it another way: Give me what Safari Reader gives me, plus a few nav links, and I'll be happy.

  • Isn't 'waste' heat from electrical devices helping heat the room? So this is only a waste in places that are too hot and use fans or a/c to compensate.
  • by Megahard (1053072) on Thursday April 19, 2012 @06:00PM (#39739551)
    Set your background to black, and <blink> all your text so it only displays half the time.
  • by identity0 (77976) on Thursday April 19, 2012 @08:43PM (#39741177) Journal

    How about less Java, flash, and videos?

    CPU and network still takes power, too...

  • by dutchwhizzman (817898) on Friday April 20, 2012 @02:34AM (#39742991)
    What about the amount of energy used to generate the page at the web server? Big, dynamic web pages requiring lots of database hits, disk IO, cpu cycles cost more energy to generate. Large pages cost more energy to transmit over networks. Complicated javascript pages, flash and java content cost more energy to generate on the computer that has to render them to display them. The same applies for compressed media, like images, sound and movies. Animated media costs more than static media too to display. Has anybody looked at those factors?

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