Power Consumption

Discussion in 'Mac Basics and Help' started by lanervoza, Oct 23, 2007.

  1. lanervoza macrumors member

    Aug 8, 2007
    As someone who is concerned about power consumption (both in terms of cost and the environment) and also about hard drive life, I am wondering if it is better to leave a computer sleeping or to shut it down completely every time I'm not using it.

    I have a powerbook g4 right now, and am thinking of a MacPro soon (for audio). Currently, I leave my powerbook plugged in most of the time, closing it to sleep when I'm not using it. I've heard that harddrives last longer if you don't shut down all the way, which may or may not be bogus (which is why I ask).

    But, if it is true that HDs last longer if you don't shut down all the way, how great is the power consumption of a powerbook just sleeping. Clearly it is getting juice from the wall and running minimally, but how different is that compared to it being off and getting juice from the wall?

    Do you sleep or shut down in general?

  2. acearchie macrumors 68040


    Jan 15, 2006
    Personally I think sleep is one of the fantastic thing that macs have over the windows hibernate, if I want to save the display or just shutup my comp for a few minutes or a few days I close the lid and when I open it up its if I havent moved straight away, whereas with hibernate you might as well turn it off it takes so long to boot back up!
  3. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    I work at an alternative energy research lab, so I've done a reasonable amount of experimentation and reading on the subject.

    First, from the hard drive's perspective sleep is functionally identical to powered down--either way the platters aren't spinning and the heads are parked. Only difference is whether the drive's circuitry is partially powered or not, and I can't think of ANY way that would realistically affect lifespan of a drive.

    Now, spinning a drive up and down may, in THEORY, reduce the lifespan of a drive... but at this point I don't think it's a realistic problem. Thing is, modern drives (particularly laptop ones, since they are expected to power down as often as possible) are built with the intention of being powered up and down repeatedly. In fact, for a while there at least, Hitachi/IBM was saying that their consumer drives were only rated to be on 8 hours a day.

    If you were spinning the drive up and down once a minute, that would probably be bad for it. But in practical use I don't think you'll likely notice it--heat, more than mechanical wear, is what generally kills drives these days. If you want anecdotal evidence, my first-gen G5 tower has been woken and slept at last 5-10 times a day since I bought it (over 4 years), and neither of its two hard drives have failed. In fact, the stock drive is my internal backup and is set to sleep on inactivity, so it probably goes through a couple dozen power cycles a day.

    In the lab I manage, the computers are mostly set to sleep the drives when inactive, which amounts to a dozen or more sleep-wake cycles, and out of around 20 machines I've seen two drive failures in the past 7 years, both OLD Quantum 10GB units that had been in service for around 5 years.

    So the bottom line is, don't worry about the effect of "normal" sleeping of your drives--it may affect life, but not enough to worry about.

    Second question: Depends a lot on the computer.

    On a laptop, sleep is VERY efficient, since they're designed to last quite a while in a sleep state on the battery. It uses slightly more power than shutting down and unplugging the power brick, but not really worth bothering with in my opinion, and I'm extremely environmentally conscious and energy-aware.

    Desktops are a different matter; older desktops generally draw a fairly large amount of electricity even when off, and actually pretty much the same amount when asleep. My old G4 tower, for example, used about 8W when "off" but plugged in, and maybe 10W when sleeping. So there was almost no point in shutting down unless you were going to unplug it or turn off the power strip (which isn't a bad idea as a means of avoiding parasitic loads, actually).

    The G5s, however, are built differently--there's some sort of contactor in the power supply that reduces the "off" power draw to very nearly zero, so there IS an advantage to shutting those down even if you don't turn off the power strip.

    I haven't gotten my hands on a Mac Pro to measure yet, but I'm guessing they're similar.

    Bottom line: Don't worry too much about sleeping your laptop whenever you're not using it, not really worth powering down a laptop versus sleep, but if your desktop is going to be off for more than, say, an hour, it may be worth shutting down to save some energy (particularly at night), and you can save a little extra by turning off the power strip.
  4. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    Here we go; I just found some measurements I did recently on some newer Macs, for reference:

    My MBP 17", 1st gen, 2.16GHz Core Duo draws 0.0W when off versus 2.0W when asleep. (Draws about 30W when idle and 80W when both cores and the GPU are maxed.)

    A 17" Core Duo iMac has very similar numbers, except for a 47W idle (probably because of the desktop-sized drive and maybe brighter screen).

    A Core Duo Mac Mini is 0.0W off, 1.5W asleep, 20W idle, and 35W maxed.
  5. flopticalcube macrumors G4


    Sep 7, 2006
    In the velcro closure of America's Hat
    New iMacs draw 2.7W on sleep. MacBooks and PowerBooks will be less.

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