One question that new Mac users often ask is whether they should shut down their computers at the end of the day or just let them sleep. The quick answer is that sleep is better for your Mac, and in today’s Tech Tip we’ll show you why it’s better to just let your Mac go to sleep than shut it down each day.
Shutting Down Your Mac Keeps It From Running Maintenance Tasks
The main reason for letting your Mac sleep instead of shutting it down is that your Mac can’t perform maintenance tasks during the night if you shut it down. macOS does a lot every night while your Mac isn’t being used and it is “sleeping”. Apple actually has a term for this sleep mode — “Power Nap”.
So what does it do during a Power Nap?
- Mail receives new messages.
- Contacts keep up to date with changes made on other devices.
- Calendar receives new invitations and calendar updates.
- Reminders keep up to date with changes made on other devices.
- Notes keep up to date with changes made on other devices.
- Documents stored in iCloud keep up to date with changes made on other devices.
- Photo Stream keeps up to date with changes made on other devices.
- Find My Mac updates the location of the Mac, so you can find it while it’s asleep.
- VPN on demand continues working so that your corporate email updates securely. (Power Nap supports VPN connections that use a certificate to authenticate, not VPN connections that require entering a password.)
- Mobile Device Management can remotely lock and wipe your Mac.
If your Mac is plugged into AC and taking a Power Nap, it will also do the following:
- Software updates are download.
- Mac App Store items (including software updates), download in the background.
- Time Machine performs backups.
- Spotlight performs indexing.
- Help Center content updates.
- Wireless base stations can wake your Mac using Wake on Wireless.
While your Mac appears to be sleeping, it’s actually doing a lot! The good part of all of this is that when you get back behind the keyboard and you’re ready to start working, your Mac wakes up quickly from sleep and is ready to get to work. There’s no need for it to go through the startup procedure, and it has already done all of the maintenance jobs it needs to do, so it’s ready to roll.
Mac users new and old often say that their Macs are running slowly, and when asked they usually say that they’re shutting down the Mac every night. It’s not surprising that the machines seem slow, as the Mac needs to run through all of the maintenance tasks it should have been doing while sleeping.
What Macs Support Power Nap?
Most Macs built since the early 2010s support Power Nap:
- MacBook (Early 2015 and later)
- MacBook Air (Late 2010 and later – requires OS X Mountain Lion v10.8.2 and later)
- MacBook Pro (all models with Retina display)
- Mac mini (Late 2012 and later)
- iMac (Late 2012 and later)
- Mac Pro (Late 2013)
How Do I Enable Power Nap?
Owners of any of the Macs listed above should have Power Nap enabled by default. To make the Mac “go to sleep”, you can select “Apple menu > Sleep” from the menu bar, close the screen on a MacBook, MacBook Pro or MacBook Air, or move the cursor into what’s called a Hot Corner.
Hot Corners are defined in the Desktop & Screen Saver system preference. In the lower right corner of the preference pane is a button for Hot Corners. Click it and a diagram showing the four corners of the primary display appears — each corner can have something assigned to it.
In the screenshot below, Put Display to Sleep has been selected for the lower right corner of the screen. Using the mouse or trackpad to place the cursor in the Hot Corner puts the device to sleep.
To make sure that your Mac has Power Nap enabled, go to “System Preferences > Energy Saver.” You’ll see the following preference pane, and just need to ensure that Enable Power Nap is checked.
Am I Wasting Energy or Contributing to Climate Change By Not Shutting Down My Mac?
If you’re energy-conscious, you might be wondering if you’re wasting power by putting your Mac in Power Nap mode instead of turning it off. Well, it turns out that your Mac uses energy even when it is plugged in and turned off!
You can find out exactly how much power your Mac uses by visiting the Apple Product Environmental Report page. Near the bottom of this page, you can find environmental reports for every product Apple has made since 2009, and that information includes just how much power your device consumes.
I use a 27-inch iMac with a Retina 5K Display as my primary computer. When it is idle (that is, not actively performing any tasks) and the display is turned on, it uses 69.1W of power. Put that iMac to sleep, and it uses only 1.22 W of power. Turning the Mac all the way off, but keeping it plugged in, power use goes down to 0.24W.
The difference in power consumption between sleeping the Mac and turning it off is only .98 W, meaning that over a year, I’m using an additional 5.7 kWh (kilowatt-hours) of power (assuming I actively use the Mac eight hours per day). At the current average residential electricity rate in my part of the country (12.04 cents per kWh), turning off that Mac each night would only save me about $0.69 per year.
That 5.7 kWh also adds only about 5.68 lbs of CO2 to the atmosphere per year. Considering that burning a gallon of gasoline creates 19.6 pounds of CO2 and the average car currently gets about 22 miles per gallon, just driving .26 miles would create an equal amount of CO2 as is generated to power a sleeping iMac instead of turning it off.