I'm using a
MGE EX20 UPS, good for 2000VA and max 1400 watts. All I have connected are 2 Hagen 301 power heads on it, that when the tank level drops, they start aireating the water. They will run for a long time. I have not experienced any long outages yet, so I could relocate/hook up a heater if needed. I could run my whole system, but don't see the advantage.
My bigger problem was the entire dining room and my office were one the same breaker. 2 tanks, and 2 computers and all the lights. So I just finished putting in a 20A dedicated circuit for my 120g and I sleep much better. I have been thinking about this for a long time, but on Monday, it triped and no one was arround for nearly 24hrs. So my tank temp fell to 70 from 78-80 normaly. No loss of life this time!! But made me get my ass in gear at put in the circuit.
Lee