Is it safe to leave your Mac plugged in and always on?

Posted:
in General Discussion edited August 2021
Charging and power habits are key to keeping your Mac in good shape, but the question of whether certain practices are "safe" -- like leaving a MacBook plugged in all the time -- can be complicated.

Credit: Andrew O'Hara, AppleInsider
Credit: Andrew O'Hara, AppleInsider


Many Mac owners leave their computers on all of the time, for example. Additionally, a good percentage of MacBook users likely use their devices in "desktop" mode constantly.

In general, both practices are safe. However, when it comes to leaving a MacBook plugged in all the time, the answer is a bit more complicated. Here's what you should know.

Is it okay to leave my Mac on all the time?

In short, yes. It's okay. However, you may notice a bit of performance lagginess creeping in over time.

It's generally considered a good idea to restart your Mac every now and then. Some programs -- particularly those are that poorly written -- can have memory leaks that cause performance issues over time. Single-bit errors in RAM can also creep in when your Mac isn't rebooted. A large percentage of these single-bit errors are induced by ionizing radiation from cosmic sources, and they accumulate with time.

A quick reboot will generally mitigate these admittedly minor issues.

Is it okay to leave my MacBook plugged in constantly?

It's probably fine to leave your Mac laptop plugged in all the time -- with a few caveats.

Batteries are consumable components that chemically age over time. Factors like charge cycles and heat can degrade the battery, and leaving a Mac plugged in and charged to 100% constantly may result in reduced charging capacity or a swollen battery in the long term.

It's generally a good idea to keep your battery from sitting at 100% for too long. This is especially true if you run your Mac hot with graphically- or CPU-intensive apps.

However, that's where Apple's Optimize Battery Charging feature can come in. The mechanism, introduced in macOS Big Sur, delays charging past 80% when your Mac is constantly plugged in.

The feature is supposed to learn your habits and stop charging when it isn't necessary. It'll know when you unplug your MacBook and time the charge cycle to keep it at 80% until you need it charged to 100%.

There's no way to directly control the feature beyond an on and off switch. And it can be finicky. It's a good idea to check in and see if it's actually learning your charging habits and stopping the charge from passing 80%.

In other words, you don't want your MacBook left at 100% for too long, but Apple's battery feature can help. If it isn't working properly or you have a macOS version that doesn't have it, try to cycle your battery at least once a month.

Apple also recommends updating to the latest software, keeping peripherals disconnected when not in use, and optimizing the Energy Saver settings to maximize battery performance.

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Comments

  • Reply 1 of 23
    maestro64maestro64 Posts: 5,043member
    Yep we never shut down our Mac desk top, it only goes to sleep at the end of the day, it can be months before a restart happens. I do from time to time run maintenance utilities to clean up logs files and such and make sure everything is working fine. I have done this for years with no ill effects. We run a 2012 Imac 27" to give you and idea and only had to replace the HDD because it start to die, replaced it with a 2TB SSD and now the computer is like new. Thinking about replacing it with the new OSX 12 coming out which will render the compute obsolete from a software upgrade stand point. 


    I can tell you PC can not deal with being left on, my work PC has to be shut down all the time otherwise it get laggy or just begins to misbehave
    rare commentpulseimagesseanjF_Kent_D
  • Reply 2 of 23
    maestro64 said:
    Yep we never shut down our Mac desk top, it only goes to sleep at the end of the day, it can be months before a restart happens. I do from time to time run maintenance utilities to clean up logs files and such and make sure everything is working fine. I have done this for years with no ill effects. We run a 2012 Imac 27" to give you and idea and only had to replace the HDD because it start to die, replaced it with a 2TB SSD and now the computer is like new. Thinking about replacing it with the new OSX 12 coming out which will render the compute obsolete from a software upgrade stand point. 


    I can tell you PC can not deal with being left on, my work PC has to be shut down all the time otherwise it get laggy or just begins to misbehave
    maestro - we are finally updating to the new 24" from our 2011 (we did two SSD upgrades) and only because software support is really vanishing.  But with 10 years from a desktop that is still going strong (speedy, reliable, etc.) and has pretty much powered on for the entire 10+ years, I can't complain about finally being pushed to buy a new machine.  I'm glad to see I'm not the only one who has been able to hold onto an iMac for so long.  And it's easier for us than you - we have a 21" so the screen will be bigger, not smaller.
    watto_cobra
  • Reply 3 of 23
    shaminoshamino Posts: 527member
    My Mac mini is never powered off.  It reboots when Apple pushes out a system update that forces it, but it otherwise remains running 24x7.  I've been doing this with my desktop systems for well over 20 years with no problems.

    And I'm certain that this contributed to the longevity of my hard drives, back when my systems were using hard drives.

    My Mac laptops don't normally get shut down, but I do put them to sleep (by closing the lid) when I'm not using them.  I only power them off when I travel, since I don't want a sleeping computer in my bag - I'm concerned that some glitch might make it wake up and drain the battery.

    WRT Windows, my work PC is a Windows laptop.  I rarely power it off either, but system updates tend to force a reboot about once every week or two.  I do log out (quitting all my apps) at the end of every day.  For what I use this computer for (Microsoft Office, basic web browsing and VirtualBox (hosting Linux VMs), the system has been very stable doing this for years.
  • Reply 4 of 23
    davdav Posts: 115member
    my 2011 iMac is left on 24x7, still running strong (display goes to sleep).  no issues with any components (256GB SSD & 1TB HD), I just can't upgrade the OS, because of the graphics card (Radeon HD 6970M 2GB). 
    Not sure when I'll upgrade, the latest iMac I don't find compelling, and the tower is too expensive.
  • Reply 5 of 23
    jdwjdw Posts: 1,334member
    I've personally come to think it is most prudent to shutdown and then leave my mid-2015 15" MBP unplugged throughout the day at home while I am at work for the following two reasons:

    1. Battery Bloat is real, which I talk about in my video here.

    2. If there is ever a battery fault (arguably, extremely rare), a fire could be triggered in your absence, which could have catastrophic results for your home.
    jSnivelypulseimagesronnwatto_cobra
  • Reply 6 of 23
    darkvaderdarkvader Posts: 1,146member
    So, the 15" 2012 MBP I'm typing on right now has spent the last few years plugged in and turned on pretty much 24/7.  It's mostly become the bed laptop, because I've got a couple newer machines that are a bit lighter... who am I kidding?  It needs a new battery, and I haven't gotten around to ordering it yet.  It's a much better machine than either my 2018 MBA or 2017 13" MBP.  They've all got 16GB RAM, but this is the only one with 4TB storage, real USB ports, FireWire, and ethernet.  Also the display doesn't crack if I'm a bit rough with my bag.

    I should probably go ahead and order the battery.  It's sitting in my iFixit cart, I've just been putting it off.
  • Reply 7 of 23
    maestro64 said:
    Yep we never shut down our Mac desk top, it only goes to sleep at the end of the day, it can be months before a restart happens. I do from time to time run maintenance utilities to clean up logs files and such and make sure everything is working fine. I have done this for years with no ill effects. We run a 2012 Imac 27" to give you and idea and only had to replace the HDD because it start to die, replaced it with a 2TB SSD and now the computer is like new. Thinking about replacing it with the new OSX 12 coming out which will render the compute obsolete from a software upgrade stand point. 


    I can tell you PC can not deal with being left on, my work PC has to be shut down all the time otherwise it get laggy or just begins to misbehave
    Which maintenance utilities do you use?
  • Reply 8 of 23
    Macs actually stop charging the battery around 100% (around 80 with optimized charging) and are provided power solely from the wall adapter. So it’s perfectly fine to leave it plugged in. I’ve tested this too by looking at the cycle count over a month and it stayed the same. 
    shaminowatto_cobra
  • Reply 9 of 23
    I was told by an Apple specialist that leaving my MBP 16” plugged in all the time would degrade the battery over time. 
    watto_cobra
  • Reply 10 of 23
    pvonkpvonk Posts: 8member
    My last two MBPs were always plugged in. They were essentially desktops; I hardly ever closed the lid as each sat on a laptop holder, the kind that is elevated (eye level).  Unfortunately each developed an expanding battery that eventually made the bottom of the metal case expand (ie no longer flat). Happened to the first one after 4 years, followed by the new replacement MBP after 2.5 years. I now have a Mac mini.

    I have used macs at home and traveled with them maybe 3 weeks per year. 
    watto_cobra
  • Reply 11 of 23
    jdb8167jdb8167 Posts: 626member
  • Reply 12 of 23
    I hope the EU makes mandatory that all companies allow to block charging to 60% or 80% (or disabled). I have an Asus laptop that has such software (but came not installed...) and it's fantastic, after 5 years and the battery is as new!

    I wanted so bad that ALL Smartphones and laptops would allow that, for example my S20 Ultra makes a full day from 80 to 30%, so if I want to charge just up to 80% over night, why can't I ?! The same goes for all companies... (and most people change phones or laptops as soon as the battery doesn't work well, so they have no reason to protect the battery too much...)
    caladanian
  • Reply 13 of 23
    I'm using a MacBook in clamshell mode pluggged in 24/7 with the free AlDente app to limit charging to 60%. Works great.
    caladanianwatto_cobraFrazzlesMeteor
  • Reply 14 of 23
    I left my 2016 Macbook Pro plugged in most of the time.  Thirteen months in, it refused to charge the battery  (no Apple Care).  I took it to my local Apple store where they diagnosed a bad charging circuit and noted that the battery only had something like 10 charge cycles on it.  They somewhat apologetically charged me $700 for a full motherboard replacement and advised me to charge it more often before the replacement warranty ran out.
    watto_cobra
  • Reply 15 of 23
    It's generally considered a good idea to restart your Mac every now and then. Some programs -- particularly those are that poorly written -- can have memory leaks that cause performance issues over time. Single-bit errors in RAM can also creep in when your Mac isn't rebooted. A large percentage of these single-bit errors are induced by ionizing radiation from cosmic sources, and they accumulate with time.

    A quick reboot will generally mitigate these admittedly minor issues.
    Considering how little time it takes to boot a modern SSD-equipped computer and the ability of MacOS to reopen apps and windows just as they were when you shut down, it makes no sense to not reboot at least once a week. Just do it during a bathroom break if you must. It'll be up and running before you even get back.
    watto_cobra
  • Reply 16 of 23
    blastdoorblastdoor Posts: 3,278member
    Regarding bit errors and cosmic rays —

    this has always sounded like a problem to worry about but I’ve never seen a clear quantification of the issue in terms that are relatable to me. There’s a Google study from several years back that I’ve seen cited but I find it hard to understand.

    if this is an issue that can really affect me in a noticeable way then I’d love apple to adopt ECC RAM across their lineup. They could do for ECC RAM what they did for IPS monitors — ie, move the industry forward. 

    But only if it’s a real issue.

    watto_cobra
  • Reply 17 of 23
    omasouomasou Posts: 572member
    jdb8167 said:
    Optimized charging works for me.


    What is in the battery.sh script? Did you write that yourself?
    watto_cobra
  • Reply 18 of 23
    omasouomasou Posts: 572member
    My MacBook Pro 16" is plugged into two LG 5K displays 24/7 unless, I remove it for some reason to work remotely.

    Typical restart is when Apple pushes an OS update.
    watto_cobra
  • Reply 19 of 23
    I can tell you experience that leaving a computer with a lithium ion battery chemistry at 100% charge state for several months is really bad for the battery's health. It resulted in the battery not holding a charge when I finally unplugged it (the voltage output was erratic). Even after trying to cycle the battery and recalibrate the laptop's battery firmware to match the new output curve, the battery's capacity was permanently cut by over 60%, far worse than if I had simply used the battery and cycled it all the time. I suspect the battery's voltage output would suddenly drop, causing the laptop to read it as a sudden change in capacity (from 55% to 10%), in some cases, suddenly shutting off the laptop.
    watto_cobra
  • Reply 20 of 23
    crowleycrowley Posts: 10,453member
    My MacBook reboots itself more than half of the time when I disconnect my eGPU, so I've taken to shutting it down whenever I want to disconnect instead of going through an error inspired reboot.  I wouldn't reboot very often otherwise, but macOS being a bit crap means I reboot quite often.
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