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Display Power Consumption: CRTs Versus TFT-LCDs

Display Power Consumption: CRTs Versus TFT-LCDs
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An increasing number of flat panel displays are based on LED backlighting, and their manufacturers aren't shy about promoting the technology's benefits to power consumption. We checked the claims to see if the promised savings are worth emphasizing.

New LCD flat panel displays are constantly reaching record lows in power consumption: 50 W, 40 W, and even 30 W are sometimes achieved in displays as large as 24” these days. The most important variable in display power savings is the backlight technology. Today, we have fluorescent lighting transitioning to light-emitting diodes (LEDs). We grabbed all of our test lab's LCD monitors and two old CRTs, pitting them against each other in a power consumption shootout.

Display Power Becoming Important

As of late, we've written a lot about power consumption on the system side, where usage is most noticeable. Processors and graphics cards were particularly blatant consumers a few years ago. Nowadays, the trend (especially in Europe) is mostly toward more environmentally-friendly components.

Green computing has forced even the largest corporations to rethink and refocus. We have low-power processors, motherboards, memory modules, hard drives, and even high-efficiency power supplies. Many things have changed, but you still need to look at every product individually to decide whether or not it’s truly efficient.

Interestingly, displays were largely neglected in this "green refresh." Part of the reason was that, ever since LCDs displaced CRT displays, the  typical PC utilizes more power than its attached monitor. However, this is changing rapidly. Enthusiast PCs, gaming systems, and workstations still often consume more than 100 W at idle and much more under load. But the majority of PCs sold are business and mainstream systems, and the average power consumption in this group is dropping fast thanks to aggressive optimization.

Display Power Higher Than System Power?

As a result, mainstream PCs that don’t sport discrete graphics and multi-core processors consume reasonable amounts of power. In the article Build a 25 W Performance PC Using Core i5, we proved that a system with above-average performance does not have to draw more than 25 W at idle. Since most 20" or higher flat panels consume 30 or 40 W, it's likely that your display will chew up more power than your nettop or mainstream system.

We decided to run a little analysis on the following displays from our test lab:

CRT:

  • Iiyama Vision Master Pro 454 (19”, 2003)
  • Sony Multiscan G420 (19”, 2002)

LCDs:

  • 19” Benq FP937S (2005)
  • 20” Samsung SyncMaster 204B (2006)
  • 24” Samsung SyncMaster 245B Plus (2008)
  • 19” Philips 190BW9 (2009)
  • 22” Acer P225HQL (2010)
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  • 30 Hide
    Anonymous , August 19, 2010 8:32 AM
    Although this is a useful article, I think your advice about ditching CRTs is misguided. Just because a new LCD uses less electricity doesn't mean it is automatically more environmentally friendly. You have to consider the environmental impacts of the production of the monitor.

    If you use your monitor 6 hours a day, it would take ~10 years for the savings in electricity consumption to offset the initial cost of a new LCD. It would likely take at least as long to offset the environmental impact of the production of that LCD (I don't feel like running a life cycle analysis for a comment but this is usually the case).

    There are many reasons to switch to an LCD, but saving the environment shouldn't be one of them. The best thing for the environment is to use what you already have until it's worn out.
  • 18 Hide
    mikewong , August 19, 2010 7:13 AM
    Ah! Haven't seen a monitor review from Tom since a long time.
    This is not really a review but it's better than nothing.
    Thanks Tom!
  • 14 Hide
    vjineo , August 19, 2010 12:18 PM
    welanand The best thing for the environment is to use what you already have until it's worn out.


    Couldn't have said it better.
Other Comments
  • -6 Hide
    Hupiscratch , August 19, 2010 6:25 AM
    I´m currently operating my SyncMaster 2493HM at just 10% brightness and is looking great. It can even diminish heat emissions from the screen to your face.
  • 14 Hide
    Scanlia , August 19, 2010 6:35 AM
    CRT's have a nice and high screen refresh rate, good for playing old games.
  • 13 Hide
    beans4you , August 19, 2010 6:36 AM
    brightness reduction can save you power consumption yes. I also like the idea of web designers using black backgrounds, its a fact that white backgrounds (like toms >.>) require your monitor to use more power than dark. :D 
  • 18 Hide
    mikewong , August 19, 2010 7:13 AM
    Ah! Haven't seen a monitor review from Tom since a long time.
    This is not really a review but it's better than nothing.
    Thanks Tom!
  • 12 Hide
    stewartwb , August 19, 2010 7:14 AM
    I'm not sure that a white background matters much for LCD monitor power consumption, except for HDTVs with a matrix of LEDs that get turned off behind black areas. Normally, the backlight is turned on to whatever brightness level the user selects, then the LCD panel selective filters (blocks) that white light to make various colors. If anything, showing a solid-black screen image would require slightly more electricity to force those pixels dark (pure white would require no electricity for the pixels, since it's blocking nothing). Also, a solid-black picture would absorb all of the backlight, which would convert that light to heat inside the monitor rather than allowing the light to escape.

    From the article, I assume the power required by the backlight trumps the power required to drive the LCD filter portion of the monitor.
  • 9 Hide
    zelog , August 19, 2010 7:15 AM
    But you can't beat CRT for movies or gaming, there's just so much more detail. Gaming Example: With LCD, experienced people will notice someone hiding in the shadows because they see "something" that usually isn't there. A CRT monitor will show the whole person fully visible, because the CRT handles the darker shades on dark backgrounds much better. Or maybe I just need to get a newer LCD.
  • 30 Hide
    Anonymous , August 19, 2010 8:32 AM
    Although this is a useful article, I think your advice about ditching CRTs is misguided. Just because a new LCD uses less electricity doesn't mean it is automatically more environmentally friendly. You have to consider the environmental impacts of the production of the monitor.

    If you use your monitor 6 hours a day, it would take ~10 years for the savings in electricity consumption to offset the initial cost of a new LCD. It would likely take at least as long to offset the environmental impact of the production of that LCD (I don't feel like running a life cycle analysis for a comment but this is usually the case).

    There are many reasons to switch to an LCD, but saving the environment shouldn't be one of them. The best thing for the environment is to use what you already have until it's worn out.
  • 9 Hide
    belardo , August 19, 2010 8:42 AM
    My previous monitor was a semi-pro Samsung 19" CRT, which I ran at 1600x1200. It was huge, heavy and was glad to get rid of it... but I needed an LCD that was JUST as high and res and affordable.

    As Zelog says about some advantages of CRT... sure, if comparing to LCDs made before 2008... the "ripping" effect can be easily fixed and very rare nowadays. One of the reasons I didn't want an LCD is that some games had to run on various resolutions... which would look like crap. But even with my trusty slow ATI 4670, I play almost ALL games in 1920x1200 on my Samsung 24" 245B (like in this review) which I bought in 2008.

    I'd never go back to a CRT... the text is never PIXEL crisp. My eyes are not hurting anymore. As my monitor aged, it developed issues and sometimes noise... also my son scratched OFF some of the anti-glare coating on my CRT and it was bugging me. I waited until he got a bit older before I replaced it. ;) 

    Oh, same kid (at age 3+) had a 19" 4:3 Dell LCD I got for $50. It recently died (meanwhile, my 1999 Samsung 15" LCD still works for tech work), so I bought a $110 ASUS 20" wide-screen LCD with LED back lighting. I don't like todays extra-wide screen displays, but this younger monitor easily has a better picture than my Samsung... but I ain't down-grading on size or resolution ;) 


    What I want in 2~3 years from now... is something like an iphone-rez desktop monitor.
    That is about 26" wide, but has a resolution of 3200x2000. Imagine how sharp and awesome that would be... retina display. *I* BET Apple will be doing that with their computers soon. Seeing the pixels is the next thing to go.

    PS: Death to glossy LCD displays!
  • 13 Hide
    Anonymous , August 19, 2010 8:50 AM
    Oh how I miss 85 hz!!!!
  • 13 Hide
    Transsive , August 19, 2010 8:57 AM
    LCDs have so many shortcomings
    - blur/ghosting (very important for games, not that bad with 120Hz)
    - most only handle 60Hz (60 fps in games)
    - viewing angles (horrible with TN)
    - color changes it's brightness across the screen surface (again TN)
    - backlight bleeding
    - horrible blacks
    - some LCDs buzz
    - some have input lag issues

    Other cons might include: only one native resolution, dead or stuck pixels, lack of aspect ratio control

    What's good about LCDs?
    - HD resolutions
    - power consumption
    - thickness and weight
    - design
    - less eye strain (no flicker, although the blur gives me headaches)
    - possibly higher contrast ratios
    - digital connections

    And 1680x1050 is a 16:10 resolution...

    My next LCD will be an ISP 1920x1200 120Hz monitor... if they ever show up. I've had it with TN panels, too much image degrading, you buy a gaming rig to play at high details only to have the monitor waste it.
  • 6 Hide
    Minerva , August 19, 2010 9:14 AM
    Hmmm, I run a dual 19" setup at home, with CRT's ;) 

    I still haven't found an LCD monitor that I like :(  I don't like the heavy widescreen display, in fact, I still prefer 4:3. Also I collect Vintage computers, so 4:3 CRT fits in with them quite nicely. I can just imagine how cruddy 320x240 is going to look like on a 24" LCD.

    I don't know what the "bleeding" is like these days on LCD's as that used to be a huge issue on the older stuff.

    Come to think of it, the only LCD that I own is the one on my HP 6910p work laptop :? I have 2x 17" and 3x 19" and they are all CRT :D 
  • 0 Hide
    icepick314 , August 19, 2010 9:53 AM
    transsiveMy next LCD will be an ISP 1920x1200 120Hz monitor... if they ever show up. I've had it with TN panels, too much image degrading, you buy a gaming rig to play at high details only to have the monitor waste it.


    for those who are interested in ISP panels...

    http://www.pchardwarehelp.com/guides/s-ips-lcd-list.php

    unfortunately it doesn't show what refresh rate those monitors have....mostly likely 60Hz...
  • 1 Hide
    pertshire , August 19, 2010 10:08 AM
    Stupid question, when you said reducing the brightness to save power, are you talking about the back lighting level or the actual brightness level? I usually keep the backlighting low and brightness and contrast high thinking brightness has nothing to do with power.
  • 7 Hide
    helmutcheese , August 19, 2010 11:52 AM
    Sony FW900 F.T.W

    16:10 24" CRT (22.5" Viewable) Max 2304x1440 @ 85HZ

    Good for Nvidia 3D as it only needs be 100HZ on CRT or lower RES 1 notch and go for 1680x1050 @ 120HZ.

    Gaming at 1920x1200 100HZ with proper blacks and full colours and zero input lag with no need for V-Sync so no need to enable laggy Triple Buffering which affects Online MP Gaming.
  • 0 Hide
    nebun , August 19, 2010 12:14 PM
    transsiveLCDs have so many shortcomings- blur/ghosting (very important for games, not that bad with 120Hz)- most only handle 60Hz (60 fps in games)- viewing angles (horrible with TN)- color changes it's brightness across the screen surface (again TN)- backlight bleeding- horrible blacks- some LCDs buzz- some have input lag issuesOther cons might include: only one native resolution, dead or stuck pixels, lack of aspect ratio controlWhat's good about LCDs?- HD resolutions- power consumption- thickness and weight- design- less eye strain (no flicker, although the blur gives me headaches)- possibly higher contrast ratios- digital connectionsAnd 1680x1050 is a 16:10 resolution...My next LCD will be an ISP 1920x1200 120Hz monitor... if they ever show up. I've had it with TN panels, too much image degrading, you buy a gaming rig to play at high details only to have the monitor waste it.


    they have been out for years...look at dell and apple
  • 14 Hide
    vjineo , August 19, 2010 12:18 PM
    welanand The best thing for the environment is to use what you already have until it's worn out.


    Couldn't have said it better.
  • 1 Hide
    ihs97 , August 19, 2010 12:56 PM
    beans4youbrightness reduction can save you power consumption yes. I also like the idea of web designers using black backgrounds, its a fact that white backgrounds (like toms >.>) require your monitor to use more power than dark.


    True, but reading large walls of white text on black backgrounds is an eye-strain and a half.
  • 1 Hide
    gto127 , August 19, 2010 12:59 PM
    I'm currently using a Hitachi HM-4721D 21 inch monitor that I've been using since 1998. No blurriness all text is razor sharp. I have it on for about 5 or 6 hours a day since 98. It might save chump change to switch to a LCD but I wouldn't trade it for one.
  • 0 Hide
    Wolygon , August 19, 2010 1:07 PM
    beans4youbrightness reduction can save you power consumption yes. I also like the idea of web designers using black backgrounds, its a fact that white backgrounds (like toms >.>) require your monitor to use more power than dark.

    Not really for most monitors as they generally don't have the ability to shut off light to sections of the screen like Plasmas. Although for some of the new ones and LED backlits this applies.
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