After years of running my own servers and pretty much leaving the power source to lady luck I have now installed a UPS (uninterruptible power supply) on my main server. The entire system is always backed up every night. The power has gone off a couple of times in the past and I have "got away with it" but now if the power goes off, the UPS battery keeps the server alive for up to 1 hour, but I have set up the software to auto shut down the pc 5 minutes after the mains power goes off. Just tried it by pulling the plug on the wall, not a flicker ! Marvellous. Should have done this years ago but just never got around to it.
I got my first UPS over 10 years ago after a transformer nearby my apartment blew and caused me a lot of issues. I now have three, one for each PC but also a UPS system just for the phone system because mine comes from the cable company and I have a phone base with wireless extensions. A lot of people think that the phone from the wall is still usable because it comes from a different power source and, while that may be true on the surface, most people have cordless phones now and those don't work when the power is out. As a side bonus, the UPS is located so that the hardware from the cable company and the wireless router are backed up along with the phone base (none of these take much power either). So when the lights go out I can still use my PC, phone and internet for at least a half-hour to an hour if necessary. Add a light in there and you can read.
Where I used to live the power would go out due to the high winds knocking tree parts (and entire trees) into the power lines so having a backup came in very handy. Normally this didn't cause the power to stay off, but even going out for a single second can still fuck up a PC.