Almost same discussion here:
http://www.marinecolorado.org/forums/showthread.php?16057-Generators-for-the-winter
I have a Neptune Apex, and two 24v Tunze power heads on a UPS that will run for an hour. In that time, I get an email, wife's phone get's text alerts notifing us of an outage. I can try to remote in two different ways to verify the power is out if we're not at home. Also, I have two PennPlax Air Battery pumps that are plugged in and not running when the power is on. As soon as the power goes out, they turn on for the display for O2.
http://www.aquariumguys.com/silentairpump.html
For long term, meaning indefinetely, I bought a Briggs 10Kw (12Kw surge) generator for the whole house. It is sized to power my AC and everything else (how I sold the idea to the wifey). Also had an electrician install a seperate electrical pannel so I can hook it up, switch it over, and everying ((including everything in the reef, lighting, pumps, heaters.....)) has good clean power. Funny thing is I've used it once only since purchased. Peace of mind I guess. Considering there is 2K of coral and fish, I sleep and travel better knowing I have all the protection. This coming April will mark 7 years I've been in the hobby. I think in that time I've experienced 20 power outages, and have though this through. Murphy's law withstanding, I feel I'm protected