Just installed a UPS system for my computer, not that I needed it but I'm the only one at work with it. Hahaha.
I got the APC (American Power Conversion), Back-UPS C S 500. Meaning its capacity is 500VA, capable of running a desktop PC, a 17" LCD screen and 19" LCD screen simultaneously, and that's only 60% of it's power capacity.
A UPS system acts somewhat like a battery but it can only last for about 15 minutes. It's works in such a way that in case of power failures, the computer will automatically shut down nicely. Just like how a laptop battery operates.