Power doesn't fail often in Germany but just as luck had it, I experienced two failures in a row in the past year that rendered my cloud services at home out of service for a couple of hours. Needless to say that both incidents occurred at the least convenient time, i.e. while I was traveling.
So far, I've stayed away from uninterruptible power supplies (UPSes) as the last one's I've seen were bulky and had a noisy fan. But recently, I discovered the APC ES-700, a small UPS the size of a shoe box without active cooling that perfectly fitted my needs.
Despite it's size it can drive equipment that requires around 40 watts for around 70 minutes before it shuts down. Just like its big brothers it has a USB port for status messages and control input and the interface is compatible to Linux's APCUPS daemon that is easily installed. Apart from letting me query the status of the UPS from the server, the softare also logs power failures and automatically shuts down my Owncloud server before the battery is empty. No noise, open source software on Linux that is easy to use, it couldn't be any better. Two thumbs up!
The screenshot on the left shows log entries generated after the software installation while the UPS was not yet connected and some real messages once the setup was in place.