I forgot to put the daughter warning in the guide. :)
When I first started programming (before the days of hard drives), I had my home computer plugged into the only convenient outlet. After about 4 hours of coding, a friend came over and asked why I had the light on in the middle of the day. He flip the switch off that controlled the outlet I had my computer plugged into. My program instantly vanished, never to return.
My first battery backup cost $600 and the piece of mind was worth every penny. I have never used a computer without a battery backup since, unless I was willing to lose whatever I was doing.
During the last storm, we lost power for an hour and a half and my main server never missed a beat. One of the big advantages of Linux servers is you don't have a monitor sucking up power.