If you’ve spent a bundle on your hardware components and don’t have a UPS (no, not the shipping company, that’s uninterruptible power supply) you might as well just be throwing money out the window. Any fluctuations in power can damage your computer’s components and will deteriorate hardware over time. More exactly, the following problems can occur (taken from WikiPedia):
UPS’s have been in use on the corporate side for many years, protecting large computer systems, telephone systems, etc with a large battery backup. The great thing is that several manufacturers offer the life-saving devices for home and small office use. You can use them for anything that uses an electrical outlet, not just computers. The battery backup isn’t nearly as long as the ones that companies use, it’s actually a different technology, but if your power goes out and your not home the software that comes with most of them will automatically save your work and shut your computer down after a certain number of minutes. Even better, most of the UPS’s come with great warranty coverage.
Thanks to HowStuffWorks you can see that there are two different types of UPS’s. A standby UPS is what home users/small offices and mid-sized companies use. It switches over to the battery in a matter of milliseconds once a problem is detected. A continuous UPS is usually a mammoth thing where the computers are always running off the battery for extremely clean power. I saw one of these large systems in use in a server room on a personal tour of one of the Sun Microsystems campuses.

I purchased a CyberPower CP550SL / AE550 (pictured above) a couple years ago, currently only $53 on NewEgg, and I’m extremely pleased with it. Half of the outlets have surge protection and the other half are surge/battery backup. In the apartment building I’ve been living in for the past year the lights have a tendency to flicker every once and a while (I’m not sure why) and the UPS does a great job at protecting against these power sags. There have also been a couple times where the power has gone completely out when I’m at my computer and it works like a charm. The battery backup takes over and I have plenty of time to quit what I’m doing and shut down.
If you’re really paranoid or want to back up a lot of devices with a UPS you can do just that because of the large scale that is offered. For example, just looking at the CyberPower brand (which seems to only do home and mid sized company UPS’s) you can get a 230 watt for $34 and at the opposite end you can get a 1500 watt for $380. Just when you thought it couldn’t get any better most UPS’s come with a connected equipment guarantee. The model I purchased comes with a $75,000 guarantee. Other popular brands include APC, Belkin, OPTI UPS, and Powercom.
If your lights ever flicker from large appliances such as dish washers or power tools that means the power to all devices is being affected. I think plenty of people are aware of power problems and have surge protectors but maybe not as many are aware of the inexpensive but essential device that is dumb not to have. Every PC user should own a UPS, especially if you’ve spent a great deal of money on it.