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Thread: LCD Monitors save electricity (True/False) ? ? ?

  1. #1
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    Default LCD Monitors save electricity (True/False) ? ? ?

    I sometimes hear sales personnel promote energy savings as one of the benefits of using an LCD monitor. I am curious as to how true this is. I'm also curious as to the existence of a numerical value to how much energy savings is produced.

    Example... 19 inch CRT vs a 19 inch LCD... Do we really get 50% energy savings as claimed by the sales staffs?

    Any body know how to calculate stuff like watts X hours = ???..... something like that...

  2. #2

    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Generally that is a true statement, especially when comparing LCD to CRT. I don't have any actual figures (you can search the internet for these), but thr power requirements for running a high-end CRT are quite high.

    LCD is also in most cases more efficient then Plasma, but Plasma's are getting much better..

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    mostly true, but some big LCD screen like Dell 30" 3007WFP can use up to 177W
    Sony Alpha 700 hobbyist

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    If you're comparing apple to apple 30" LCD vs 30" CRT, yes is True.

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    A simple end user verification is feeling the amount of heat decipated by the LCD or CRT...CRT edmits more heat than LCD which is a clear sign CRT uses more power

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    My CRT monitor is rated at 100W and a viewsonic LCD monitor is rated at 35W.

    Does this automatically mean that I get 65% savings... or is there something else to calculate ? ? ?

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    Senior Member jnet6's Avatar
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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by arampan
    My CRT monitor is rated at 100W and a viewsonic LCD monitor is rated at 35W.

    Does this automatically mean that I get 65% savings... or is there something else to calculate ? ? ?
    kinda of...

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    yes it's right. not only that. CRT contains mainly coils and are inductive in nature. this sort of consumes 'more' electrical power even though we're not billed for this part of consumption. The LCD is mostly solid state and is less inductive therefore has better power factor. am I confusing you?

    In short, yes it saves power.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  9. #9

    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    True. A CRT is basically an oscilliscope which is firing electrons to project the image, so you have a rough idea how much power is required to generate all the electrons to be fired out just for basic display.

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by yanyewkay
    yes it's right. not only that. CRT contains mainly coils and are inductive in nature. this sort of consumes 'more' electrical power even though we're not billed for this part of consumption. The LCD is mostly solid state and is less inductive therefore has better power factor. am I confusing you?
    You certainly picked up bits and pieces in school, but what you write is nevertheless nonsense.

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by yanyewkay
    yes it's right. not only that. CRT contains mainly coils and are inductive in nature. this sort of consumes 'more' electrical power even though we're not billed for this part of consumption. The LCD is mostly solid state and is less inductive therefore has better power factor. am I confusing you?

    In short, yes it saves power.
    CRT tube fires an electron via a delta gun array which are directed by magnetic fields to hit the phosphorescent material on the screen. The CRT generates 625 line (that's what we use in Singapore PAL system) per second. CRT use very high volatages as high as 32,000V.

    LCDs on the other hand are liquid crystal which are electrically charged to and change the way light pass through it.

    PS: If I made any mistake my apologies

  12. #12

    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    LCD does save electricity compare to CRT

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by LittleWolf
    You certainly picked up bits and pieces in school, but what you write is nevertheless nonsense.
    i see.. sorry then.. so I guess LCD uses more power then? Now I'm even more confused myself.

    From what smtan24 said.. assuming he's right and that my memory still serves me well.. the electron generated had something to do with a high tension coil? and the X-Y deflection is done by another 2 coils? These 3 are the most inductive components in the CRT.

    LCDs on the other hand alters the state of crystals suspended in a liquid. This is controlled by a digital bit stream. and the LCD is lesser an inductive laod than CRT. During one of my lessons as a school boy, I was being spoonfed (without my own research to support the teacher's claim) that LCD eases on the power factor as it was less inductive and being less inductive was better for power suppliers. He was drawing the example of a typical computer lab that has 100+ CRT versus LCD.

    And now with everyone going into power factor corrective devices, the excess capacitor banks they have earlier planted to counter inductive loads are now posing a problem.

    And from the other bits and pieces, Sg Powers do bill for inductive loads for factories but not home users.

    Maybe you can shed more light on this matter? it doesn't hurt to correct my nonsense.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    BUT becoz LCD radiaion is lower and more pleasing to your eyes and produces less heat...... you'd probably be playing more games and using it for longer hours....

    Hence.... LCD uses more electricity?

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by Zplus
    BUT you'd probably be playing more games and using it for longer hours....

    Hence.... LCD uses more electricity?
    there is logic there too

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by yanyewkay
    i see.. sorry then.. so I guess LCD uses more power then? Now I'm even more confused myself..
    The nonsence is the part on how you explain CRT draws more power because it has an inductive load. CRT does consume more power than LCD but it has nothing to do with it being an inductive load.

    Quote Originally Posted by yanyewkay
    From what smtan24 said.. assuming he's right and that my memory still serves me well.. the electron generated had something to do with a high tension coil? and the X-Y deflection is done by another 2 coils? These 3 are the most inductive components in the CRT.
    Having coils in a piece of equipment does not automatically make it an inductive load on the whole. The coils are inductive, that's for sure, but they are not simply connected directly to the mains. The combined load may or may not be inductive as seen by the mains supply.

    Quote Originally Posted by yanyewkay
    LCDs on the other hand alters the state of crystals suspended in a liquid. This is controlled by a digital bit stream. and the LCD is lesser an inductive laod than CRT. During one of my lessons as a school boy, I was being spoonfed (without my own research to support the teacher's claim) that LCD eases on the power factor as it was less inductive and being less inductive was better for power suppliers. He was drawing the example of a typical computer lab that has 100+ CRT versus LCD.
    An LCD monitor has internal switching power supply that uses coils also. Using your argument then it should be an inductive load also.

    Quote Originally Posted by yanyewkay
    And now with everyone going into power factor corrective devices, the excess capacitor banks they have earlier planted to counter inductive loads are now posing a problem.

    And from the other bits and pieces, Sg Powers do bill for inductive loads for factories but not home users.
    Since PUB do not charge domestic users for drawing phantom power, I really wonder what good are power factor correction devices for? What problems are these devices posing? Care to elaborate?

    Having poor power factor means that there is more power wasted on the transmission lines (due to higher current resulting in higher I^2 R losses). For domestic users since the total power consumption is comparatively low it costs PUB more to try to charge individual households separately for poor power factor than the wasted energy (furthermore the cost may have already been averaged and absorbed into the per kWH price). For industrial consumers the power consumption is high enough to make it worthwhile to penalise those who do not implement their power system properly.

    Quote Originally Posted by yanyewkay
    Maybe you can shed more light on this matter? it doesn't hurt to correct my nonsense.
    Most of the excess power consumed by CRT (compared to LCD) is transformed into heat.
    Last edited by roygoh; 22nd March 2006 at 06:06 AM.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  17. #17

    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    I remembered I read somewhere that for a same sized LCD, the power consumed is only 10% of an same sized CRT. Is it really that much less?

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by roygoh
    Since PUB do not charge domestic users for drawing phantom power, I really wonder what good are power factor correction devices for? What problems are these devices posing? Care to elaborate?
    You are right that since Sg Powers do not charge domestic users for phantom power the purpose of having power factor correctors are questionable in homes. However, these("PFC" enabled devices and some claiming "Active PFC") is the basis for many of the 'power saving devices' being sold in many place in sg, I'm not sure if you've seen such devices that plugs into the wall socket. The problems caused is that Sg Powers have some capacitor banks placed around sg to balance the mostly inductive load of appliances(fan, previously incadescent bulbs and i remember clearly TV belonging in the list of inductive loads). When consumer products turn more towards switching power supplies instead of the common transformer based power supplies, the overall load is now turning more capacitive (less inductive) and the capacitor banks previously installed are now proving to be counter-productive.

    Quote Originally Posted by roygoh
    Having poor power factor means that there is more power wasted on the transmission lines (due to higher current resulting in higher I^2 R losses). For domestic users since the total power consumption is comparatively low it costs PUB more to try to charge individual households separately for poor power factor than the wasted energy (furthermore the cost may have already been averaged and absorbed into the per kWH price). For industrial consumers the power consumption is high enough to make it worthwhile to penalise those who do not implement their power system properly.
    Poor PF due to TL losses cannot be passed onto the customer (although I cannot gurantee nor confirm what the power industry practices, someone has to pay for it right?).

    lifted off the net because I no longer have my schooling notes:
    Power factor is the ratio between the KW and the KVA drawn by an electrical load where the KW is the actual load power and the KVA is the apparent load power. It is a measure of how effectively the current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.
    If I'm not wrong.. one of the cause of apparent load is from inductive devices.
    ok I think I have sprouted even more nonsense from my bits and pieces again but I cannot resist in tech discussions. I guess both yourself and LittleWolf are from the power industry or experienced working professional engineers? Please do correct me if I have misunderstood or mis-represented any information
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  19. #19

    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    hm. I always tot that power consumption is measured in the wattage of the equipment is used.. Correct me if I'm wrong..

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    Default Re: LCD Monitors save electricity (True/False) ? ? ?

    Quote Originally Posted by yanyewkay
    However, these("PFC" enabled devices and some claiming "Active PFC") is the basis for many of the 'power saving devices' being sold in many place in sg, I'm not sure if you've seen such devices that plugs into the wall socket.
    I haven't seen them, but it sounds fishy. About the only way I can imagine to achieve this in a small plug-in device would be to incorporate an inverter. That would fix the power factor, but also increase energy consumption (due to the limited power conversion efficiency of such devices). If it was so easy to correct for it, SP wouldn't have all those cpacitor banks, right?

    The problems caused is that Sg Powers have some capacitor banks placed around sg to balance the mostly inductive load of appliances(fan, previously incadescent bulbs and i remember clearly TV belonging in the list of inductive loads).
    One typical inductive load is fluorescent lighting. In contrast, incandescent lighting is about as non-inductive as it gets. In fact, because of their low inductance, lightbulb-like devices are used to measure high frequency currents that most other meters can't. Inductive loading due to incandescend lamps occurs when transformers are involved, as in the case of low-voltage halogen lamps that have become popular only in recent years - even then, well-designed systems aren't that bad. Most TVs and CRTs nowadays use switching power supplies; the main inductive component is usually the degaussing coil that runs only for a split second after power-up. Of course, if you leave your TV on "standby" instead of turning it off after use then it might feed all its standby power from a small auxiliary transformer, but at a low level.

    Phantom power isn't "consumed", and inductive (or capacitive) loads are not the reason why some appliances consume more or less power. (It does though pose a problem for electricity distribution networks, as the currents may trip fuses, saturate transformer cores, cause voltage spikes when turned off, and cause transmission line losses.) Industrial price structure does usually not only reflect the cost of the energy, but also the strain on the distribution network and the predictability of load patterns.

    The reason why I reacted a bit harsh to your earlier statement is the rationale. By the same logic, organic matter would have to be considered hazardous waste - life is largely based on phosphorus, and elementary phosphorus plus some of its compounds are hazardous.

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