Power to the Apple

The story goes that an irate customer brought their new iMac back to the Apple Store, ticked off because the thing wouldn’t power on. A longtime (but unhappy) PC user, they had finally been badgered enough by their Mac friends to spend the extra money for a brand new iMac with Bluetooth keyboard and mouse, upgraded hard drive, extra memory, Retina screen, and so on. The works.

But it wouldn’t start up. 

The specialist who was handling the issue apologized to the customer and ordered up a replacement. Then, while waiting for it to be brought out, she started to verify the issue and process the exchange. She unpacked the iMac on a training table, pulled out the power cord, and plugged it into an outlet. 

“What are you doing?” asked the customer.

“Just have to verify the problem to process the return,” replied the specialist as the screen lit up and the boot sequence chimed in.

The customer was shocked. “The box says it’s wireless.” 

Power is something we all take for granted these days. Plugging in and charging have become so much a part of our daily routine that it’s unlikely we would ever make the wireless power cord mistake. But at the same time, we don’t think much about the quality of the power we feed our Macs or the consequences of an unexpected power failure. 

The macOS is a busy operating system as any visit to the Activity Monitor can prove. There are tasks running most of the time, some simply monitoring processes and some that are performing maintenance or ongoing tasks like copying data. Time Machine, iCloud Photo Library, and 3rd party services like BackBlaze all happen in the background when the Mac is otherwise unoccupied. And not just with the Mac itself, but with any EHD’s or networked drives attached. This is why it’s best to do an orderly shutdown of processes from the Menu [Apple>Shutdown…] than to use the power switch or key commands [Control+Option+Command+Power or Eject] to force a quick shutdown. An orderly shutdown does some housekeeping and logging off as part of the process to ensure that everything is in place when you start up again. 

Which brings us to the question of an unintended shutdown because the power went off. 

Fortunately, portable Macs - MacBook, MacBook Air, MacBook Pro - are well equipped for losing power because they run on batteries and can sense when the battery is getting low. When that happens, the macOS creates a snapshot of the running processes and open windows and goes into a hibernation state until power is restored. 

It’s the desktop Macs - iMac, Pro, Mini - that really need a little help. They are the most vulnerable because they rely on AC power and are generally left on continuously, even if in Sleep mode. Therefore, desktop Macs are routinely exposed to power failures and spikes that portable Macs are not, risking data corruption and problems with the macOS over time.

The solution comes in the form of backup/uninterruptible power supplies. A BackUPS is like a giant power strip with a built in battery to take over if AC power fails and gives you time to save and shut down your Mac in an orderly way. They come in different battery sizes to support more powerful or multiple Macs on the same BackUPS and generally have 6+ plugins. Two of the biggest suppliers are APC [apc.com] and CyberPower [cyberpowersystems.com]. Both companies have good information to help you decide which model is most appropriate for your situation. 

Another benefit of a BackUPS is line conditioning/surge protection. Desktop Macs are sensitive to fluctuations in power so in older homes, places prone to thunderstorms, or areas that suffer from brownouts and spotty power service, line conditioning ensures that an even, constant power supply is running your Mac. A BackUPS that has line conditioning circuitry will likely dedicate some of the plugs to that and the rest will draw off the standard battery backup circuits. The thinking is that while it’s important for your Mac CPU to have line conditioning, it doesn’t matter for an external monitor or a router. 

You also need to think about your typical power failure. You can certainly get big enough batteries to run a newer, more energy efficient Mac for a couple hours or more, and that may be smart if it’s a regular occurrence. Generally speaking, though, a BackUPS is expected to supply enough power for you to complete a task and do an orderly shutdown. No more than 15 minutes. If it’s in your home, you will likely hear the alerts and be able to do that manually. But if your workstation is in an office or you are routinely away, you will want a system that supports unattended shutdowns. As it happens, the macOS Energy Saver panel can recognize when a Back-UPS is plugged into your Mac and you can have it automatically shut down the Mac based on one some criteria. 

Manufacturer sites will have guides to help you decide what size and model of Back-UPS you need, but it basically comes down to 2 things: 

  • What is the combined power consumption of all devices?

  • How long do those need to run for safe shutdown or to complete a typical operation?

You can find the power consumption by doing a Google search for “iMac (or whatever) power consumption,” and the manufacturer will give you a runtime calculator of each Back-UPS. 

Here is an example of an Apple support doc for iMacs: 


Here is an example of a CyberPower Back-UPS:


So in this case, if you had a new 27” iMac using 262W(max)/71W(idle) and an older 21.5 iMac using 74W(max)/33W(idle) of power, the CyberPower CP1500 could run them both for between 20 minutes (335W total at max cpu) and 80 minutes (104W total at idle) before shutdown. 

One last thing is that buying a good Back-UPS from a leading company ensures that when the battery finally gives up - and it will - you can buy an original or 3rd party replacement battery rather than replace the whole unit. 

Obviously, there are many devices that don’t need battery backup although any electronics can benefit from surge protection and/or line conditioning. So when making your Back-UPS choice, consider which devices can just go into a wall socket (lights, chargers, DVD drives, shredders), which should have surge protection (monitors, backup RAID and NAS arrays, routers, printers), and which need full battery/line conditioning (computers, active working drives, network switches). 

For computers, a Back-UPS is like insurance in a box. Whether you rely on your devices as a business tool or to manage your personal photos and documents, managing the power in a consistent way can help keep everything running smoothly and safe.