How much power does my iMac draw when display is off?

Discussion in 'iMac' started by plucky duck, Apr 20, 2012.

  1. plucky duck macrumors 6502a

    Jan 5, 2012
    I would like to know roughly how much it costs to have my iMac stay turned on 24/7 with the display turned off? Its a 2011 3.4Ghz 240GB SSD 27" iMac. I would like to access photos/files/movies stored on the iMac via my iPad that's why I just leave the display on the iMac turned off, but the rest of the computer is still active.

    How much watts does it consume? I'd imagine a bit more than usual because the 3.4Ghz CPU is always running at 3.4Ghz? Or is there a way to put the CPU in a lower frequency sleep mode? I am thinking the SSD draws much less power than a traditional mechanical drive?

    I am thinking leaving the iMac on 24/7 is better than "shocking" the system by turning it on and off a few times in a day? I am worried about the capacitors or the power supply might be worn down unnecessarily by constantly turning it on and off.

  2. leman macrumors G3

    Oct 14, 2008
    My guess would be something around 50W or less. SSD use less power then HDD, but we are talking about just few watts difference here, hardly worth mentioning.

    Maybe more interesting to you: the iMac supports wake on LAN/WLAN. This means, you can send your computer to sleep but it will automatically wake up when your iPad wants to access some data (and go back to sleep thereafter).
  3. forty2j macrumors 68030


    Jul 11, 2008
    HDD's stop the motor after some time when they're not in use. There won't be a difference in power consumption in "sleep mode".
  4. Intell macrumors P6


    Jan 24, 2010
    My 20" iMac uses about 50 watts when the screen is off and idle. And about 70 when the screen is on with minimum brightness and idle.

    Intell i series CPUs have SpeedStep so that they clock down when not in use to save on power. Modern systems are much more robust and are not affected by powering on and off as much as those of the 90's and early 2000's.
  5. omvs macrumors 6502

    May 15, 2011
    I measured mine a while ago - I believe it was in the 30-40 watts with the display off, but I'll have to recheck to be sure.

    The wake-on-lan can be very useful to decrease power even further, and there's iOS apps that can be used to wake up the machine if it won't automatically wake up for you. I use one called iWakeOnLan to power up my media server, since it burns >50 watts idle.

    NOTE: In a multi-monitor mode, the power consumption of the 2011 iMac increases by another 20 watts, even in idle mode. It was noticeable enough that I went back to single-monitor config just to keep the machine cooler.

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