Power draw for 15" rMBP used as desktop

Discussion in 'MacBook Pro' started by inscrewtable, Jul 31, 2014.

  1. inscrewtable macrumors 68000


    Oct 9, 2010
    It seems to me that to charge an uncharged macbook that an 85W magsafe would draw 85W. After searching the net I am unable to find what the power draw is of a 15" rMBP is when it is fully charged and plugged in.

    Bearing in mind that it seems to charge pretty quickly while being used, and also bearing in mind that the small fan is the only moving part I was wondering if anyone here is able to clue me in on this.

    Naturally it would depend on brightness of screen and load on processors, however I'd suggest as a desktop that the screen would be near maximum and also that on average it would not be using much processing power.
  2. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    The power draw is actually more than 85W if you're doing heavy tasks on it.

    More than a few times, while working on heavy 4K video editing (and plugged in), I've seen my rMBP's battery drain bit by bit.
  3. pgiguere1 macrumors 68020


    May 28, 2009
    Montreal, Canada
    I have a mid-2012 15" rMBP (discrete graphics) currently at 100% battery, plugged and hooked to an external monitor.

    iStats menu currently reports a DC in of ~1.0A @ 20V, so if I'm interpreting that correctly, that'd be 20W. All I have open are "basic" apps like Safari, Mail, iTunes, Preview, Pages, Calendar.

    If I start Starcraft II, I get to ~2.4A @ 20V, so 48W. However that's with a 30FPS framerate cap so I'm not pushing my system at full load.

    I haven't noticed any time my system losing its charge at any moment (meaning it never seems to take more than 85W), but there were times where it would charge verrrrry slowly (or not at all), meaning it pretty much took 85W.
  4. thunng8 macrumors 6502a

    Feb 8, 2006
    Can use up to 90w when loaded..

    This review here measured 88w or so

  5. dusk007 macrumors 68040


    Dec 5, 2009
    I have a late 2013. With an external screen connected and the 750M active,
    my idle draw is 0.95A-1.0A @20V
    When typing doing not very much about 1.5A.
    Load with Flash videos and such 2.4-2.6A.
    When charging 4A.
    Full load is 3.6A-4A + something from the battery at peak.

    The power supply is always 20V +/- a bit so just multiply by 20 for the W.
    On the wall you probably would have to divide the W by 0.85 as I am guessing this is where the efficiency of the power supply should be. Could be 0.8 or around there too.

    BTW on battery the numbers are quite a bit lower but it seems to disable some power saving features when plugged in. It is still little compared to a big Desktop.
  6. El Magnificante macrumors member

    Jan 20, 2007
    How does using the rMBP like this affect the life/health of the battery?
  7. dusk007 macrumors 68040


    Dec 5, 2009
    If you only use it like this, what does it matter?
    In general anything that heats up the notebook makes the battery age faster and every once in a while you should empty the battery a little (not a full charge - full depletion is bad for it - just 20%-50% here and there).
    Regardless of how much use it gets it will grow old and faster if the computer is on and the case warmer than if it was off. Off and put in the freezer gives the battery the best chances ;) Not sure how much use the notebook is traking up space in the freezer.
  8. w00t951 macrumors 68000


    Jan 6, 2009
    Pittsburgh, PA
    My Kill-A-Watt measures 84W at the wall when fully loading both CPU and GPU.

    However, the battery also drains, so I'd guess the total system power is slightly higher than that.

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