2017 iMac i7 power consumption

Discussion in 'iMac' started by VinOrdinaire, Jul 26, 2017.

  1. VinOrdinaire, Jul 26, 2017
    Last edited: Aug 6, 2017

    VinOrdinaire macrumors newbie


    Jul 26, 2017
    Pleasant surprise on the low power consumption of my new 2017 iMac, and I haven't seen this mentioned before in other threads so I thought it might be helpful for those making buying decisions:

    Note: All power measurements are from a Belkin Conserve Insight watt-meter:

    My old machine:
    2009 Mac Mini 2.0GHz, 256GB HD, 4GB RAM: 26 watts
    Dell SP2208WFP monitor: 41 watts
    Dell 1901FP monitor: 36 watts
    Labtec LCS 2422 speakers: 6 watts
    Total dual monitor Mac Mini setup: 109 watts

    New Machine:
    2017 27 inch iMac, 4.2 GHz i7, 1TB SSD, 16GB RAM, Radeon Pro 580 graphics: 40-50 watts in light use.

    That's an efficiency improvement of about 60 watts, with all the advantages of a 5K screen and the headroom of a quad core CPU with hyperthreading, so I get the benefit of power when I need it and energy efficiency when I don't.

    I know that the Apple help site says that the 2017 27 inch iMac consumes 71 watts at idle, but that configuration was 64GB RAM and 3TB fusion drive. My system power's usage with an SSD and less RAM is a real-world 40-50 watts for web browsing and office applications, with occasional spikes to 60 or 70 watts.

    I know that I have gone from two monitors to one, but the 27 inch 5k monitor is making a great first impression. Quite easy to place two documents side by side, and much sharper resolution with a retina display.

    Speaker sound quality is excellent, by the way. Better than the freestanding speakers I was using. They have been retired.

    Fan noise is unnoticeable. It's easier to hear the Seagate portable hard drive attached to the iMac than to hear the iMac fans. I'm sure it will spool up when needed but for light use it is essentially silent.

    Conclusion: for web browsing and office applications my new computer uses about 60 watts less than my old computer, is essentially silent (lower fan noise than my old Mac Mini), and provides an otherworldly improvement in computing power.

    Your mileage may vary.

    August 6th update:

    Power consumption varies with screen brightness by about 40 watts. In a brightly lit room near a sunny window the iMac is at nearly full brightness and power consumption is at 70 to 80 watts. At dusk with room light off the iMac is at about 1/8 brightness (settings menu, Display) and power is about 36 watts. My initial measurements were likely with the monitor in moderate room light.
  2. nambuccaheadsau, Jul 26, 2017
    Last edited: Jul 29, 2017

    nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
    A very nice set up. I trust the Macwhiners do not drag you down with all the threads on here about increased power consumption, fan noise, poor retina display etc etc etc.

    Every time a new model is released the doom sayers seem to come out of the woordwork.

    Enjoy your iMac. I always go for the i7 27" model as when it comes time to update, i7 seem to sell so much quicker and for a little more doh reh meh!
  3. cynics, Jul 28, 2017
    Last edited: Jul 28, 2017

    cynics macrumors G4

    Jan 8, 2012
    Curious what it is under a load.

    Idle 63w, transcoding a video 116w, transcoding a video while playing a game (Cities Skylines) 187w.

    2013 i5-4670 (84w TDP), 24gb RAM, 1tb HDD.

  4. EugW macrumors 603


    Jun 18, 2017
  5. VinOrdinaire, Jul 29, 2017
    Last edited: Jul 29, 2017

    VinOrdinaire thread starter macrumors newbie


    Jul 26, 2017
    Thanks for the comparison.

    Once I have more software and games that will push the iMac I'll add my observations. For now Cinebench R15 shows these results:
    • at idle, 50 watts.
    • OpenGL 133.46 fps, 125-140 watts, fan speed no change at end of test idling at just under 1200 rpm, fan unnoticeable.
    • CPU 945 cb, about 150 watts, fan speed ramps up to around 2333 rpm. Fan is a slightly mechanical whirring rush, and it is noticeable.
    • CPU (single core) 190 cb, 82 watts, fan speed idling under 1200.
    The Radeon Pro 580 is clearly not stressed by this test. I will follow up after trying other software.
  6. VinOrdinaire thread starter macrumors newbie


    Jul 26, 2017
    Here's another data point for the 4.2 MHz i7 2017 with 1TB SSD and 16GB RAM:

    F1 2016 for Mac, practice session, 2560x1440 resolution, all graphics effects turned up to max, runs at 60 fps and draws 180 to 190 watts. Fan spins up while playing to about 2200 RPM give or take.

    When I turn the resolution up to the native 5K resolution of 5120x2880 the frame rate drops to 22-24.

    It will be interesting to see if Metal 2 improves 5K performance.
  7. DrOct macrumors newbie


    Nov 23, 2012
    Any chance one of you could tell me the power usage while idle with the monitor off? I'm curious to get a ballpark of what my iMac is using when it's been sitting there long enough for the screen to turn off (but isn't asleep).
  8. JohanCruyff macrumors member


    Nov 14, 2007

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