Power is unpredictable. A car crashing into a pole or a small flaw in a transformer can cause a blackout or a surge strong enough to destroy most electronics in your home. Although rare, these events can knock your computer out when you need it most. It can even cause thousands of dollars of damage.

The solution is not any mere surge protector but instead an Uninterruptible Power Supply (UPS). These big, beefy units combine a high-quality surge protector with a backup battery that will keep electronics running through a blackout (for a short time, at least). Here's what you need to think about before making the leap to a proper UPS.

How Many Outlets Do You Need?

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Like a surge protector, a UPS only has so many outlets. That's why you must determine how many devices absolutely must be plugged in. For small or home office purposes, that usually only amounts to a router, modem, and sometimes a mini server. However, for larger businesses, your needs might be greater. Generally speaking, it's a good idea to buy whatever you need plus two, as that gives you some flexibility for the future.

However, keep in mind that many UPS units only provide surge protection on some ports. The outlets powered by the battery will likely be less than the maximum number of ports. Inexpensive options often cut costs by only providing battery backup to four or six outlets, leaving the remainder unpowered. That's won't be a problem for everyone, but it can be a nasty surprise if you learn about it the first time the power goes out. Fortunately, you'll notice just by looking at the UPS whether or not it has ports without backup power.

Finally, if you're using wired data connections, look for a UPS that provides protection for them as well. This includes both old-fashioned modem and newer Ethernet connections.

How Much Power Do Your Devices Require?

 

With your outlets handled, you'll next have to ask yourself how much power the devices connected to the UPS will consume. If the devices need more power than the UPS can generate, they'll go dead, even if the battery has plenty of energy remaining. Think of it like a computer's power supply; if the wattage is lower than what the computer needs, you're out of luck.

You can find out how much power your PC (or other equipment) uses with a wattmeter, which can be purchased online for about $15. Remember to check the consumption of everything that you need to power. If you want to power a desktop PC, for example, you need to add together the wattage of the computer and the monitor.

The amount of power supplied by the unit is often written just before the letters "VA" (or Volt-Amps). Unfortunately, it's not possible to convert from VA to a recognizable number, like watts unless you know the Power Factor (PF) rating of a UPS. A very rough (and not usable) estimate would be to approximate VA as watts. So, for example, the CyberPower 1500VA can at peak, supply up to 1,500-watts of power if the PF is near 1. Lower power factors could result in a UPS that doesn't supply enough juice -- so you may want to purchase around 20% more VA than you need.

How Long Do You Need To Run On Battery?

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Now that you've handled the wattage, you should also think about how long your devices need to run. Some buyers purchase a UPS because they want a few minutes to shut down devices properly and save any work that was performed on them. Others want a UPS so they can work through blackouts which may last as long as an hour.

By the way, if you've configured Windows properly, it should automatically shut down once power loss is detected. I

To figure out how long a UPS will power the devices you'll connect, add together the wattage they draw and then refer to the product's runtime/load graph. Usually, this can be found on the side of the package or, if you're buying online, in the description. The APC BR1000G Pro, for example, can power 400 watts of equipment for about nine minutes or can power 100 watts of equipment for an hour.

What Features Do You Want?

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You might think that the features of a UPS would be simple. You plug in devices, and when the power it goes out, the battery kicks in. That's all there is to know, right?

Nope. Even basic consumer-level units offer features like disconnecting battery notification, USB connectivity and a software suite that can be controlled via PC to fine tune settings and see how much power is being consumed. A beefier "professional" unit offers even more features, such as a LED that reports remaining battery charge and runtime in minutes, and hot-swappable batteries.

Most people won't need such fancy extras, but simply knowing that they exist is important. You're paying for it, so why buy a UPS with fewer features, if all other things are equal?

How Good Is The Warranty?

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A UPS normally lasts as long as its internal battery -- and generally, that's around two-three years. The reason is that batteries decay over time, particularly when fully charged. And UPS batteries -- by default -- are charged all the time. Because of its battery, almost all warranties max out at around three years -- just long enough to cover the lifespan of the battery. Fortunately, some UPCs offer insurance on top of a 3-year warranty. For example, APC's policy includes a $75,000 insurance policy and data recovery with Ontrack -- but only on some products. Double-check before buying.

As such, I heartily recommend APC products to anyone concerned principally about their backup battery's reliability. Of their vast product selection, one of the best APC UPSes out there is the APC BE650G. Its battery is replaceable, it receives high marks from reviewers, and it offers just enough juice to keep your home office or small business afloat during a power outage. For larger power needs, though, you might need to look elsewhere.

Of course, there's the potential for gotchas, so you should probably read the warranty online at the UPS manufacturer's website before buying.

Note: To clarify, UPS batteries are designed to be serviced. Most just pop out. So when the battery fails, you normally only need to order a replacement.

Conclusion

Do you already own an uninterruptible power supply? Leave a comment letting us know about your experience. There are many UPS devices on the market, and they tend to vary from region to region, so reader tips can help add to the discussion.

Image credit: Komjomo via Shutterstock.com, Wikimedia/Zátonyi Sándor

Originally written by Matt Smith in September of 2013.