Maybe lightning strikes, literally. Maybe a wind storm takes out some power lines. It could be a blazingly hot day, and one too many people cranks the A/C up to 11. Or maybe there's a flood or fire in an underground vault, taking out a bunch of circuits. The result: no power.

If you're working at a desktop computer when the power goes down, that could mean trouble when your monitor goes dark. It's happened to me a few times – both at home and at a client site. I've always lost some work; sometimes more than just some.

There are two major types of UPS available. Standby UPS is the most widely used in homes and small businesses. They're small, and fairly inexpensive. A standby UPS is a essentially a battery and a power inverter. The power inverter converts the battery's DC propecia patent expiration date current to AC current, which your equipment can use. When the standby UPS detects a power failure, it kicks in the power inverter (usually within a few milliseconds) and switches over to battery power. The battery in a standby UPS only holds enough power to run your equipment for a few minutes – just enough time to save your files and power down properly.

Widely used in server rooms and other mission-critical areas is continuous UPS. A continuous UPS, again, consists of a battery and an inverter. However, equipment runs off the battery. The battery is constantly recharged using conventional power. The advantage of a continuous UPS is that there is no delay in failing over to battery power. You get constant power.

First, how much protection do you need? If you only need to protect one computer, then look for the UPS that best fits your budget. A home user, for example, could probably get away with a lower-end UPS. If you're running a small business out of your home or have a central home server and a few computers, then budget for a few more units.

Next, consider how many devices you'll be plugging into the UPS. At the very least, this will be two – your computer and a LCD Monitor. A decent UPS usually comes with four outlets. You can also get systems that have 6, 7, 8, 10, or 12 outlets. Just remember that the more devices that you plug into a UPS, the faster the battery will drain.

Think about some of the extra features of a UPS and whether or not you'll need them. For some people, a bare bones UPS might be the way to go. Others might need more features, like a voltage regulator or the ability to initiate a shutdown at a defined time after power goes down. You definitely should read the information on a vendor's Web site, or talk to a customer service representative, to learn more about the extra features.

Find a UPS that's right for your equipment. Pay attention to the VA rating of the UPS system. The VA rating is the amperage of your equipment multiplied by your voltage. You can usually find the amperage on a sticker on your equipment – like one at the bottom of a laptop computer. Then, tally up the VA ratings of all of the equipment that you plan to plug into the UPS. Some people suggest that once you get the cumulative VA rating, you should buy a UPS that has a VA rating 20% or more higher than the one you calculated. Good advice, especially if you will be adding equipment in the near (or not so near) future. For most home users, though, you can probably get away with a VA rating 10% to 15% higher.

If you need more help figuring out which UPS is right for you, there are tools available on the Web. APC, one of the top makers of UPS systems, has an online selector that lets you choose the right UPS for your needs. You can find online selectors here and here.

Something else to consider is price. You can get a decent UPS for around $30 (USD). A good one will cost $50, and probably more. If you'll be buying more than one UPS, factor the overall cost of those units into your budget and choose your price point accordingly.