Right now I use PC style UPS for my tanks (both are 12g or less). They work splendidly for a few hours with just a power head and heater on.
tbittner I see where you aren't worried about heater being on UPS because wife likes the house very warm. If you lose power do you NOT lose heat too?
We sell large residentail generators here where I work and they aren't very expensive for a minimal unit to run essential house items and your tank essentials. But you gotta pay an electrician to come hook them up. And even with a generator there is still some type of lag (depends on the unit) between power out and generating full power (could be a few secodns up to 45+ seconds depending on the unit). I would still use a battery back-up system to filter and cover that momentary lag. Just my 2 cents
Allen