What a lifesaver! When the electrical power suddenly vaporizes, the files you were working don’t disappear. This reasonably priced unit gives you 6 to 17 minutes to close down your computer, depending on the size of your equipment. That’s plenty of time to get through an orderly shutdown. In sleep mode my Mac G3 and 21 inch monitor once lasted 5 hours during a blackout when I was away. Brands of gear seem pretty interchangeable. The one I use, the APC Battery Backup 500VA, also has surge protection for the phone or cable modem line. The price of a battery backup, or Uninterrupted Power Supply (USP) as it is called technically, has dropped sufficiently so that every computer should have one. (Except laptops, which have their own built in supply.) Where power is especially unreliable, or where you want to power printers as well, you can buy more capacity.
[*A newer model, the 550VA, is also available for $60 from Amazon. -- SL]