Back Up Your Power Supply

February 2011 — Tip of the Month

Last month, I stressed the importance of backing up your data. This month, I want to encourage you to back up your power supply. That's right, you can actually back up the electrical power to your computer. If you've ever lost unsaved work due to a power failure, you understand just how valuable this can be.

In order to back up the power to your computer, you need a UPS, or "uninterruptible power supply." This device acts like a surge protector, but also includes a battery, which serves as a backup power supply in case the primary AC power fails. A UPS, or "battery backup" device can be a lifesaver when you are writing a paper, working on an important project, downloading a large file, or playing an online game. Since the battery backup power kicks in as soon as a major power fluctuation happens, it can protect against brownouts (brief power reductions), as well as blackouts, where power is lost for a long period time.

Most UPS devices will begin to beep when they are on battery backup. This lets you know the electrical power supply has failed and the battery is currently powering your computer. It also means you only have a limited time before the battery power runs out. The runtime of the battery depends on how large the battery is and how many devices you have connected to the UPS. For example, if you only have a computer and monitor connected to the UPS, it will last longer than a UPS that has a computer with multiple monitors, external hard drives, routers, and other devices connected to it.

When choosing a UPS, the most important specifications to check are 1) the number of outlets, and 2) the VA rating. Most UPS devices have battery backup outlets and surge protection only outlets. Both these outlet groups protect connected devices against power surges, but only the battery backup outlets will supply power to the devices in the case of a power failure. Therefore, you want to make sure you connect your computer, monitor, router, and modem to the battery backup outlets. Peripherals like your printer and speakers can be plugged in to the surge protection only outlets. When buying a UPS device, make sure it has enough battery backup outlets to support all your primary devices.

The VA rating determines the "load," or maximum wattage a UPS can handle. It's important to know that only the devices plugged into the battery backup outlets count towards the load. Typically the maximum wattage supported by a UPS is roughly 60% of the VA number. Therefore, a 550VA UPS will support a maximum load of around 330 watts. This might be enough for a basic home computer, but may not be sufficient for a high-end workstation or a computer with multiple displays. If you have a high-end computer, a 750VA UPS is probably a better choice.

Personally, I use an APC Back-UPS XS 1500, which is rated at 1500VA and supports a maximum load of 865 watts. A few years ago, I bought a UPS with a VA rating that was too low for my system. The result was that my computer began shutting off unexpectedly. Therefore, I learned the hard way that it is best to get a UPS that has more capacity than you think you'll need.

- Per Christensson