Powering Your Mac: Power Filters and UPS

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November 25, 2021

Powering Your Mac: Power Filters and UPS

Howard Oakley:

Providing your Mac with a reliable filtered AC supply is very important to protect it from sustaining damage during electrical storms, when there’s utility maintenance underway, or some idiot trips a circuit-breaker or pulls the mains plug.


Most Macs are well-protected if the UPS keeps them going long enough to allow an orderly shutdown – a minute or two at most. It’s far better for a Mac to be given that chance than to have no UPS at all.


When that’s connected to your Mac, the Energy Saver pane should recognise it and offer both display options and Shutdown Options, which determine how quickly your Mac shuts down when mains power is lost and it’s running off the battery in the UPS.


There’s an important fact which can sometimes be forgotten: the USB interface on a UPS can only be connected to one Mac. If you’ve got two Macs to protect, they each need their own UPS, as one UPS can’t tell two Macs to shut down, except by SNMP, which is considerably more complex to use.

I used APC’s Back-UPS LS for many years with success, but eventually the units (not just the batteries, which I’d replaced many times) failed, and APC discontinued the design that I liked. Lately, I’ve been using a Tripp Lite, which is great except that starting with Catalina the Mac always thinks it’s out of power and needs to shut down. Now the USB connection is useless, and it’s no longer a good solution for a Mac that will be running unattended.

Some other things to consider when getting a UPS:

  • Does it have a loud fan or make a constant electrical hum noise?
  • You want a dedicated outlet for each device that needs power. Don’t plug a power strip into the UPS. Extension cables are OK.
  • See how the UPS will fit into your workspace, especially if you have a height adjustable desk, and how easy it will be to get to the controls or change the battery without moving a lot of things around.
  • Check whether the UPS sounds a constant alarm while on battery power and whether that can be configured in advance or suppressed once it’s activated.
  • Send in the registration card so that you can make an insurance claim if your connected equipment is damaged. I have not heard of anyone actually getting reimbursed, but you may as well increase your chances.

Update (2021-09-07): Although I think an extension cord will work in practice, the Tripp Lite manual specifically says that doing this will void your warranty.


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