In today's age with low power standby modes & the advanced OS X that is Mountain Lion, it is simpler than ever to go for long periods (perhaps months) without shutting down your iMac (and possibly Mac mini too).

Is it really necessary to perform a complete shut down of your Mac (and what considerations if any need to be taken account of)?

  • You should let it go to sleep as needed. If you have an Apple router it will proxy the Bonjour announced services, and wake the machine as needed. Commented May 21, 2013 at 22:29

9 Answers 9


The benefits of shutting down vs. sleeping is an oft-asked question. Over time, reasons to prefer shutting down have either been resolved or significantly ameliorated.

For instance:

  1. It used to be that shutting down early macOS (then OS X) machines caused issues with timed log clean-up routines. This has been resolved with the OS recognizing when routines haven't run and rescheduling them.

  2. Similarly, long-running systems used to exhibit instability relating to memory issues. Shutting down the computer cleared the memory, temporarily resetting things. However, memory management has subsequently improved in later versions of macOS and this is no longer a significant issue.

  3. A shut down system used to be significantly cheaper. However, advances in hardware and software have improved the ability of Macs to sleep efficiently. In 2020, a 27" iMac with Retina 5K draws 0.27W when shutdown and 1.25W when asleep (compared to 40W when idle) (source). Apple prepares environmental reports on all its devices extending back several years that you can check. Copies are available from the Environment section of Apple's website.

In addition to these changes, features like Power Nap improve the utility of sleeping Macs.

For me, I set automated sleep and wake times and almost never reboot.


Can't believe almost every one of these recommendations is saying to NOT restart your computer on even a semi-regular basis. I have a rMBP which I restart at least once a week. I also have a Early 2008 iMac that acts as a server that I restart at least twice a month. I do this b/c it allows the machine to purge unused memory and temp data that builds up over time.

I work in IT for a large, Mac-based school district. I cannot tell you the number of times that a simple restart fixes simple issues and how much better my staff's computers run if they restart once a week. On average, especially if your machine gets used quite a bit; I would recommend restarting your Mac (or any computer for that matter) at least once a week. A lot of it depends on how you use your Mac.

In the end, if you're Mac isn't a server, then restart it every once in awhile. "Always-on" is meant to be for Servers, and even then, servers have to be restarted from time to time.


No, with the exception of restarts for software updates, shutting down your iMac or Mac Mini is not necessary. You are quite correct that you can put your device to sleep for long periods of time or even leave your device up and operating without causing any damage to the device, so long as proper precaution is taken to ensure surge protection for your electronics.

An even better solution would be to provide some form of backup power supply with a USB link to your device that works in OSX so that when a power loss is detected the device will shut down properly for you to be able to resume your uptime later. Most servers or datacenters have operated this way for years already, and the difference between the service life of servers and home hardware has come increasingly closer over the last decade. The days of the recommendation being to shut your PC down whenever you aren't at it are becoming increasingly out-of-date.


It's mostly a personal preference at this point I think.

I'm happy leaving my 2012 iMac on all the time. I sleep it overnight and any time I'm away from my desk for more than a few minutes. The power consumption during sleep is extremely low; by Apple's data, only 1.03 watts, versus 0.22 W for power off (on the 27" model). Even idling it's a pretty efficient machine.


I apologize for necroposting (old thread) but I am compelled to correct one critical fact. I agree that it is generally fine to let your modern Mac run while leaving sleep and energy management to the operating system.

But... Apple does not call "Shutdown" "Idle"! From Apple directly we have: https://support.apple.com/en-us/HT201897

  1. Power consumption data (Watts) is measured from the wall power source and includes all power supply and system losses. Additional correction is not needed.
  2. "Max" is defined as the maximum possible power draw based on the computer's power supply rating.
  3. "Idle" reflects the power used with only Finder open, using the default power management settings.

TomRou read that page that he quoted incorrectly. “You can read more about this on Apple's site and select the report for your Mac.”

  • Thanks for pointing this out. I've edited TomRou's answer to correct this mistake and generally update it to be more appropriate for 2020 :)
    – pyrmont
    Commented Jan 28, 2020 at 1:01

It's not necessary... and, speaking about power consumption, it has ho sense (iMac). It was big disapoitment, when I realize (by meter), that iMac (2011) consumes 9W in sleep mode, but also 9W if it is OFF – so you have to unplug it, to have 0. Nine W – that's like one small energy-saving light bulb... :(


I have an older iMac it only draws 2W @ 240V AC once it is in sleep mode. I suspect your system is pulling closer 0.9W you may want to check it with a more accurate meter.

When my system is shutdown it is pulling well under 1W @ 240V AC


I leave all my Mac devices on all the time, has had no effect on battery life (where applicable), or performance.

  • 1
    Thank you for your answer. Please note, however, that the OP asked about two machines that don't actually have a battery. Perhaps that would change the answer a little? Commented May 22, 2013 at 1:51

Yes - turn your unit off, as opposed to Sleep or Restart, at least once per week to enable the built in Apple optimization processes designed to run at shut down and startup to do their thing. Give your units a night off. And do not leave power plugged in 24/7 to the various Macbook units.

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