IMO it boils down to 3 options. UPS, inverter, and generator.
Personally, I have an inverter and a generator on hand.
I am NOT a fan of the UPS option, because unless you buy a very oversized UPS, any amount of backup time you'll get from it is going to be for a timeframe that the tank could go without power anyway, and unless you buy a very expensive UPS, it may have trouble running powerheads.
The generator is my favorite option, because dollar for dollar, you get the most wattage and runtime for the least money - especially with those cheapo chinese import generators you can get nowadays, which are perfect for our application. Plus, you can run other stuff like your fridge, TV, even the furnace in your house if you know how to wire it up. Tank heaters won't do a pantload worth of good if the house temperature is 40 degrees...
The inverter on the other hand is cheap, easily stored, and can easily be hooked up to a car idling in the driveway for an indefinite supply of electricity.
I have both, in case my generator fails, or we lose power at night when I don't want to make a racket, I have the inverter.