How Much Power do LCD Monitors Save?

By Deane Barker on June 1, 2004

How much do you save with LCD monitors?: My wife and I are slowly switching our entire house over to flouresent light bulbs — you know, those spiral looking things? We’re doing this because we’re sick and tired of changing burnt out incandescent bulbs, and these are supposed to last so much longer. They also use a lot less power. The bulbs I got are meant to replace 60-watt incandescent bulbs, yet they use just 23 watts. Bonus.

This got me thinking about power consumption, and then about LCD monitors, since they apparently use much less power than an equivalent CRT. I have a 19” CRT that has served me well, but is getting a little dimmer with every passing month. I thought, if I I could prove significant power savings, then perhaps my wife would let me buy a nice, new flat panel.

I found this article over at CNet which, sadly, doesn’t quite prove my case, but is interesting nonetheless. The savings are there, but they’re not quite enough to justify a 17” LCD (about $400 minimum), which I would need to equal the screen area of my 19” CRT. Too bad.

…the approximate cost of using the LCD 24 hours a day is $3.74 per month. If you use this device for three years, the extended power cost for the life of the device would be $134.78.

By comparison, if you had a CRT device consuming 90 watts with the same usage requirements, its monthly power consumption would be $6.48, and its three-year usage cost would be $233.68. So simply using the LCD device for the same requirement over three years of 24-hour usage would give a savings of nearly $100. In locations with high energy costs (such as California), this savings can exceed $130 over the three-year term (assuming a $0.14 rate).

You also have to consider that these calculations assume the monitor is running 24 hours a day, which mine isn’t. It’s more like two hours. So that puts my power savings down to less than $10 over three years.

Just the other day, however, I visited a brand new customer service call center. They had all brand new equipment, including 15” LCDs on each desk. I wondered at the time how they could justify the purchase of LCDs when they’re still twice as much as CRTs and desk space didn’t seem to be an issue. But when you consider that these monitors are on 24 hours a day, perhaps the power savings is enough to influence the decision.

Gadgetopia

Comments

  1. You also have savings attributed to the decrease in heat generated by the LCD monitors versus the CRT. I don’t know the actual numbers, but a company that includes LCD monitors in place of CRTs can decrease the size of their HVAC equipment which could potentially be a significant savings.

  2. That works both ways, however. When I worked at Citibank in Sioux Falls, South Dakota, they had huge buildings that they did not have to heat through South Dakota winters because of the radiant heat given off by the equipment.

    If you swap in LCDs, then you lose that heat, and you have to start heating the buildings.

  3. Even if you’re buying one or two, shipping costs are much less. I bought a 19″ and a 15″ LCD last week from CDW and shipping was $23. Compare that to $120 for a 21″ and 17″ CRT pair that I bought last fall.

    Another factor to consider is uninterruptible power; you can get by with a much smaller UPS to power the cpu and monitor if you have LCD displays. Your wife might not see that as a reason to jump to LCD, but that has an influence on the decision process where I work.

  4. What about the loss of productivity from the eye strain and resulting headache caused by the refresh of CRT monitors? Personally, I know when working long hours on a CRT vs an LCD, I’m much more productive on the LCD becuase I don’t need to take a break just to let my eyes rest. Also, at the end of the day I don’t have a pounding headache.

  5. The Cnet article is misleading on a few fronts. Apple’s well-designed Samsung-based (I believe) 17-inch LCD uses 40W not 90W when in use and 3W in standby. A 19-inch CRT (Sony CPD-E400) with similar viewable area uses 140W while on, 15W in standby, and THREE WATTS while merely plugged in and turned off.

    So that’s at least a 70 percent savings in active use and 80 percent in standby.

  6. The call center case is interesting. While the wasted energy that comes off in heat could mean that a company doesn’t need to run the heater, this is only a saving if electricity is cheaper than the fuel used to heat the building otherwise. Any inefficiency of say 100 watts is for all practical purposes the same as running a 100 watt heater year round — probably more expensive than central heating, and since always on it fights the air conditioner in the summer so that 100w waste becomes a minimum 200w waste. Also, some one mentioned that the power savings would be greater with more monitors. However, so would the outlay for new equipment, so the cost benefit analysis for a single monitor is valid unless there was a significant volume discount (though I would agree that being used 24 instead of 2 hrs/day would make a big difference). I would assume the most convincing reason for them was the enormous saving in space. From back of the monitor to back of your chair (with some space too) changes from about 5ft to less than 4 ft, meaning that they could fit at least 25% more people in a given space. As for power consumption, I am a little dissapointed in the savings if the figures I was able to find on monitorsdirect.com are accurate. The most efficient CRT’s only require about twice the power to run as comparable LCD’s.

  7. Just got from other sources…

    You asked for specific information regarding the energy cost savings and pay- off time for a flat screen vs. a CRT monitor. As has come up in several comments, there are many specific factors that go into calculating this answer. Among them are:

    Time Usage ? how often your monitor is on (and for a CRT is it asleep or awake?), hours used per day, days used per year Energy usage ? the wattages of the specific two monitors you wish to compare Local energy costs ? the cost charged per kW by your electric provider

    While I cannot answer your question exactly (without further details), I can tell you how to make the calculation yourself.

    First, you need to calculate the kW used per year for each monitor. The energy usages can then be converted into costs by multiplying by your energy rate.
    The difference between the two costs reflects the cost savings you will recoup after using a flat screen (instead of a CRT) for one year. You can apply this annual savings to the price difference between the two models to determine how long it will take to pay off the more expensive flat screen.

    kW saved per year The Energy Efficiency and Renewable Energy Network (EREN) is part of the US Dept of Energy. At the EREN website they list the wattage of many appliances. http://www.eren.doe.gov/consumerinfo/refbriefs/ec7.html The wattage of a CRT monitor is listed as 150 watts (awake) or 30 (asleep).
    This means that in energy use, one hour of awake time = five hours of sleep time for the EPA example monitor.

    According to IBM, the T Series flat panel monitors consume 3-4 watts asleep and 30 ? 65 watts awake.
    http://www.pc.ibm.com/us/accessories/access_promo/flatpanel/tour/ Note that the awake energy use changes by a factor of more than 2, depending on screen size. For a flat screen monitor which uses 3.5 watts (asleep) and 50 watts (awake) 1 hour of awake time = 14 hours of sleep time.

    For an example solution (for a CRT) see below:

    Time Use ? hours/day: 6.5 (to account for sleep time) Time Use ? days/year: (52weeks/yr ? 2weeks vacation/yr) x (5days/wk) = 250 days/year Monitor Watts: 150 Cost per kWh: $0.07

    [(hours/day) x (days/year) x (watts)] / 1000 watts/kW = annual kWh consumption

    (kW) x ($/kWh) = annual energy cost

    [(6.5hr/day) x (250days/yr) x (150watts)]/1000 = 243.75 kWh annual energy consumption (243.75 kWh) x ($0.07/kWh) = $17 per year A CRT monitor costs $17 per year in electricity.

    Using the above calculations for a flat screen monitor with the following data: Time Use ? hours/day: 6.2 (to account for sleep time) Time Use ? days/year: (52weeks/yr ? 2weeks vacation/yr) x (5days/wk) = 250 days/year Monitor Watts: 50 Cost per kWh: $0.07 A flat panel monitor costs $5.40 per year electricity.

    To do this yourself To determine the exact answer to your question, perform the above calculations for each of the two monitors, and compare your results. To determine your annual energy usage, use the wattage values printed on the back/bottom of the two monitors you are comparing. To determine the Time Usage for a CRT that goes to sleep, use an average value of time based on the % time the monitor is awake/asleep.
    Additional Information Many resources can be found where the energy efficiency of flat screen monitors is touted. Several of these sites are mentioned in the comments. Others are: UC Irvine News, March 14, 2001 http://www.today.uci.edu/ucinews/0314f4.html

    National Renewable Energy Laboratory http://www.nrel.gov/sustainablenrel/energysaving.html

    Other Notes: Be careful when using specific energy savings figures from a Manufacturer. As shown above, there are many factors that go into these final figures, so anything quoted is just an estimate, and Manufacturers have an incentive to make their product more attractive.

    While some of the energy used by a CRT is generated as heat, a CRT is generally not as efficient as a real heater. For heating purposes it will still be more efficient to spend those kW on a heater not a CRT.

    While the EPA Monitor Power Management Calculator is helpful in computing cost savings on the basis of certain criteria, this calculation does not allow you to calculate costs based on monitor type. http://yosemite1.epa.gov/Estar/consumers.nsf/content/powercalculator.htm

    I used the following search terms: flat, screen, panel, monitor, ?energy use,? efficiency, watts, utility, cost, electricity

    Enjoy your new monitor! (whether it’s a flat screen or a CRT) While it doesn’t add to the energy savings, the flat screen sure looks cooler :)

  8. Another consideration for some people is a higher cost of electricity. Some developing countries such as where I am located have much higher electric rates. My company that develops software for used vehicle exporters in Japan is based in were electricy and airconditioning is ver expensive, so I am definately planning to use flatscreens.

  9. The most important reason for me buying an LCD monitor and tv was the health benefits. The electromagnetic fields emitted from CRT Monitors and regular TVs has been shown to be pretty bad for your health. LCD Monitors emit a thousand times less electromagnetic radiation than CRTs. Here is one article you should read. http://www.scienceagogo.com/news/20040118190816datatruncsys.shtml I’m about to start work at a call center and I sure hope that they have LCD monitors because I’m not going to be exposed to CRTs 8 or more hours a day 5 days a week.

  10. Just like to add a bit of information. The energy cost of cooling a 100 watt heat souce is not 100 watts. For a fairly efficient air conditioner (12 EER or 3.5 COP) an additional 28 watts will be needed to remove a 100 watts of heat.

  11. I’ve done some rough calculations, and I think they are underestimating the cost of running the CRT monitor, and therefore underestimating the savings. I think a large CRT will consume more like 140-150 watts. In my calculations, the true savings of switching to an LCD (for a 19″ monitor operating perhaps 10 hours per day) runs more like $20 – $30 per year. Not a huge amount, but when you consider that I’ve seen some flat panel 19″ monitors for around $200, not bad. You could potentially recoup half the purchase price in 3-4 years.

  12. According to this calculator, the savings could approach $70 per year on a 19″ monitor operated for 8 hours per day. That being said, they are using an electricity rate of about $.15 per kilowatt hour. My rate is more like $.10, so the savings would be adjusted down to account for a lower rate. Maybe, $47 per year.

    Anyway, check it out:

    http://www.viewsonic.com/monitoruniversity/lcd.htm

  13. I would recommend that you actually use a device, like a Kill-A-Watt, to mesure the actual energy use. I think you will be surprised — certainly, I was. As it turns out, CRT’s are not the energy hogs that you might think they are. Our 32″ CRT TV at home uses 120 watts. A 25″ CRT at home uses 80 watts, and the 17″ CRT monitors we have measured are less than that.

    People keep buying larger LCD panels, which require some significant backlight. A little known fact is that a 36″ LCD TV can actually use MORE power than a 36″ CRT TV. Certainly when we are talking smaller sizes, the LCD saves money, but if you are looking at a fancy 26″ Widescreen LCD monitor, you are negating any energy savings.

    The theory that LCD monitors save significant energy was true when it was originally talked about — when people were buying 15″ LCD panels. Now that folks consistently buy panels that are twice that size, or are purchasing multiple LCD panels, clearly the energy savings is going away rapidly.

    In any case, actually measure your current device’s energy use, and then make your buying decisions from there. You may be surprised that the old CRT you have is actually not consuming as much energy as you thought.

  14. Hi Deane,

    Bubba is right. The actual savings actually comes if you are using an air conditioner (applicable if you are living in a warm place requiring A/C) because heat generated by CRTs is much higher than LCDs. A computer shop in our area with 15 CRTs converted to LCDs was able to save as much as $160 a month.

    But then again, if you are using it only at 2 hours a day and considering the picture quality of a CRT over LCDs, it might not be very much worth it. Picture quality of CRTs are much better than LCDs.

  15. I read the comments from begining, it was 2004, how about the LCD vs CRT comparation now, in the second half of 2009, are there any enhancements in both technologies? I think that now we can speak about other data, concerning power consuption and energy cost

  16. 19 inch monitors range from $5.60 to $9.90 in annual electricity cost according to CNET reviews (assuming 70/30 sleep to active ratio and the U.S. average of $0.1135 cost per watt.)

    The calculations in the thread above, estimating how long it would take for energy savings to justify the LCD monitor cost, all ignored the most significant cost factors: the purchase cost of the CRT and the relative lifespan of the LCD vs CRT (possibly up to twice the lifespan).

  17. With how cheap CRT displays are available as secondhand (even practically brand new ones are being dumped or thrown away), the cost justification of lower power consumption of an LCD goes away. I mean, how can you beat $10 for a monitor, even if it does use more power?

  18. I also consider that lcd is much better then crt according to power consumption space requirement, saving etc. But i thing that CRT emit rays those rays are dangerous for the people who use the PC for a long time. But according to repairing point 0f view spot and line on the lcd screen are not removed while crt can be repair

  19. lcd is much better then crt according to power consumption space requirement, saving etc. But i thing that CRT emit rays those rays are dangerous for eyes. But according to repairing point 0f view spot and line on the lcd screen are not removed while crt can be repair

  20. It’s not worth it to switch.

    You have to consider all the effort that is involved with getting rid of the old CRT and purchasing and installing the new LCD.

    Replace the CRT when it dies.

  21. On the other hand, if you live in a cold environment, the LCD monitor could help warm up your room & -reduce- your electric bill. :-D

  22. yes useing flouresent light bulbs use less energy sure but your eyes soon start war watring your head going lose hair

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