You will have to watch the AC output, MOST inversters (like for computers, etc..) have a different output (Square wave) which will make the motors hum more thand a standard AC (Sine Wave) output, also more expensive.
I have a std. Computer 800Watt backup on our ours and it will run 15-20 mins, but the motors will hum a bit, won't hurt it.
You could probably remove the built in battery and hook a larger deep cycle (car, marine,etc.) battery to extend the time.
Here are some inverters and ideas
http://www.dcacpowerinverters.com/pure_ ... rters.html