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  1. #1
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?

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    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    Is that true? That seems like a lot, but never bothered to compare it to my 4.5 yr. old PC.

  2. #2
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    T_O_P12's Avatar
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    Where did you read this?

  3. #3
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    chas_m's Avatar
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    No, you did not read correctly.

    The iMac tech specs page clearly says that that **MAXIMUM** continuous power is 241W for the 21.5 version.

    Nearly all of this is of course due to the screen. The 24" Cinema Display, for example, uses 212W as max. continuous power.

    So, if we were to imagine the iMac as two separate components and assume the 21.5" screen used 200W max continuous, that would mean the COMPUTER part would use a maximum of 41W. And again, *maximum* means exactly that -- in routine use it would use less power than that.

    This is probably why the iMac -- alone among all-in-one computers of this size, as far as I can tell -- is EnergyStar rated.

    If your 4.5-year-old PC is hooked up to a CRT monitor (as would be appropriate for its age), then you can rest assured you are using WAY WAY more power to run the monitor there than any LCD monitor made by anyone. If you have an LCD monitor on it, you're still using more power than the iMac's LED-backlit screen at the same size and resolution.

    Here's more information on this if you're interested.

    Greenpeace themselves acknowledge that Apple has taken the lead on making their product line as energy-efficient as it can be.

  4. #4
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?

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    Good stuff, Chas.

  5. #5
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?

    Member Since
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    Well, maybe we're "splitting hairs" here? When I said my iMac will use 240 watts per hour, I was, of course, including the use of the monitor since I would seldom use the "computer" part without the screen being on. Isn't that true or am I missing something (which isn't hard to do). So, wasn't I "right" (you said I didn't read correctly - ) when I said I read the amt. of wattage is 240 Watts? Or are you saying that it's rare to use it at its maximum. If that's the case, wonder what would the "average" usage amount to in wattage per hour? (230 watts? lol) Especially, since the iMac is an all-in-one and not with a separate tower, how often does one turn off the monitor but keep the computer on anyway? Just asking ...

  6. #6
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    pigoo3's Avatar
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    Quote Originally Posted by Newbie2mac View Post
    Is that true? That seems like a lot, but never bothered to compare it to my 4.5 yr. old PC.
    Well if it makes you feel any better...if your iMac had a CRT display instead of an LCD...it would use a good bit more wattage.

    If you want to do your part to "be green"...you could either turn the brightness down as low as it will go (but still viewable)...or turn your computer off!

    Another option could be to sell your iMac & buy a laptop! I think that the low-end MacBook uses a 65 watt power adapter.

    - Nick
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  7. #7
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?

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    to chas_m:

    Your post is not entirely correct. In a Apple display it has to have it's own power source to power up and use the display. So that's the 212W you talk about. But the imac does not need 2 power sources (screen and computer). It only needs the one to to power the screen and the computer workings behind the screen. So I'm sure the power usage of the screena nd the computer in the imac would fluxuate over time.

    So my point here is a computer and seperate screen or the same computer and screen as an all in one have slightly sifferent power usages due to the fact the seperate ones need 2 power sources and extra parts for that where as the all in one needs only one power source for everything.

    Just a really minor point. But otherwise what you says makes basic sense.

  8. #8
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    chas_m's Avatar
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    Quote Originally Posted by Newbie2mac View Post
    Well, maybe we're "splitting hairs" here?
    No, we're not "splitting hairs." You misread.

    "Maximum" is a word that actually has a meaning.

    Isn't that true or am I missing something (which isn't hard to do).
    Again, you're missing something. That something is "maximum."

    To achieve a use of 241W/hour, you would have to have the monitor on at full brightness, doing something like playing a complex 3D game, running the GPU and CPU at 100% all cores, plus spinning the optical drive, plus typing and mousing continuously, plus having bluetooth and internet active and functioning. For an hour. IOW, you would have to be maxing out every part of the Mac's functionality continuously.

    Do you find yourself doing that on a routine basis? No? Then the 241W/hour idea isn't accurate and doesn't apply.

    If that's the case, wonder what would the "average" usage amount to in wattage per hour?
    Apple doesn't supply that information and I wouldn't like to speculate (because it depends on a LOT of factors, starting with screen brightness), but there's a device called a Kill-A-Watt that you can buy and use to measure this.

    You still haven't explained a) why this is important and b) why you feel it is high in comparison to any equivalent machine. As previously explained, LED-backlit screens use less power than flourescent-backlit LCDs, which it turn use a lot less power than CRTs. Likewise, chip manufacturers (particularly Intel) have been continuously working on reducing the power draw of their processors even while making them more powerful, meaning a computer from just a few years ago that was less powerful, didn't have all the additional features today's computers have (such as powered ports, Bluetooth and wireless cards by default, fast hard drives, faster optical drives, etc etc) drew a max combined of anywhere from 250-400W/hour.

    But the key thing to understand is that when one says "max" that's exactly what one means -- a rarely-achieved state of full exploitation of all power-drawing resources. Even older computers typically draw much less than their max power consumption -- anywhere from around 60W to their upper "max" limitations. If you're word processing on a dim screen, you're using a HECK of a lot less power than if you're playing CRYSIS on a max-brightness screen.

    So, in short, the iMac does *not* draw 240W/hour, which is what you claimed, in typical use.

    Had you actually read the link I provided, you would have learned that Apple takes LOTS of steps to minimize electrical use when the computer is "idling," which is what it is actually doing most of the time one uses it. This is why Greenpeace and the government have both given the machine high marks.

    Especially, since the iMac is an all-in-one and not with a separate tower, how often does one turn off the monitor but keep the computer on anyway? Just asking ...
    It's called "display sleep" and most of us have it available all the time. Since the bulk of what a computer does is wait for input from the user, one can set the screen to go blank after a certain number of minutes of inactivity. The exact amount can be adjusted (if one is a slow reader for example, one might set it to a longer time). Adjusting the brightness also has a dramatic effect on how much power the screen uses (and again, the screen is the major culprit of energy use). This is precisely why devices that are dependent on battery, such as notebooks and the iPhone (et al) have such quick "dim the screen" and "go to black" timings.

  9. #9
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    osxx's Avatar
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    I am surprised Greenpeace is not up in arms over gaming computers with 1000 watt power supplies.

  10. #10
    Did I read correctly? My new iMac 21.5" uses 240 W. an hour?
    pigoo3's Avatar
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    Quote Originally Posted by chas_m View Post
    there's a device called a Kill-A-Watt that you can buy and use to measure this.
    Yeah...I always wanted to get one of these (or a similar device)...for the very reasons mentioned. And not just for measuring a computers watts used...but other devices as well.

    And as mentioned...a variety of factors go into the exact watts used for a device...making exact estimates difficult without a meter.

    - Nick
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