How to configure shutdown settings with a UPS on a Mac
An uninterruptible power supply (UPS) can provide continuous power to your equipment in the event of a power outage. They can also sustain power outages (brownouts) and condition power in areas with poorly managed power grids. UPSs have been around for decades, and Apple started providing silent, built-in support in macOS many years ago. It can currently be found in system settings > energy saver on Macs that need to be plugged in, like an iMac or Mac mini. (This will be moved to system settings > energy saver in macOS 13 Ventura.)
At some level, a UPS is only as good as its integration with the equipment it powers. A modern, high-capacity UPS may provide all the power needed to keep your Mac and peripherals running during brief outages that can last anywhere from a few minutes to tens of minutes. But for outages of unknown duration, you want to define graceful shutdown parameters. While system corruption was a regular occurrence when hard drives became commonplace and before changes to macOS that improved recovery, sudden power outages are still not uncommon.
Every UPS model I’ve tested for TechHive has a USB jack or compatible port. All also offer downloadable software for macOS and Windows. However, the software is often outdated, difficult to use or too detailed. In most cases, you don’t need to change any low-level settings; In this case it is sometimes easier to use the settings on the front of the UPS.
By simply connecting one of these devices to your Mac via USB, macOS can detect its status: it can detect when the UPS has switched to a mode where it is delivering power and read the percentage of power remaining. Support is surprisingly widespread. Once connected, a UPS button will appear in the Energy Saver window. Click on it to get access to some settings and a nested dialog with more.
You can set how long the display stays active after the UPS switches to backup power directly from the tab view. Modern displays are low in wattage, but you may prefer to turn off the display early to keep your system running longer. If you find that your UPS turns on regularly, you can enable the “Show UPS status in menu bar” option to display a special power icon. Click on it to view the current UPS battery charge and other details, identical to how the battery status is displayed on an Apple laptop.
Click Shutdown Options and you can selectively enable and set three parameters that control when the shutdown occurs:
- After using the UPS battery for: Set a duration for how long your Mac should run without battery power.
- When the UPS battery time remaining: This is an estimate that macOS generates by observing the drop in level as the UPS supplies power. If you have any sense of how long it takes for our Mac to shut down, you can use that as a guide.
- If the UPS battery level is below: Expressed as a percentage, you can use this alongside or instead of the time remaining estimate.
Calculate the total wattage of your Mac and all other connected devices, and use UPS manufacturer tools to determine how long you can operate on backup power. macOS running off an SSD usually shuts down quickly – my M1 Mac mini shuts down in less than 20 seconds in most cases – you can time your own device to shut down if you’re concerned it might take longer than a minute could.
You can tweak the shutdown settings with this data to give yourself (or software working on tasks) the longest available time before being forced to go offline.
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