8amps*110v=880watts.
You'll need an 880watt inverter, probably more like 1000 because it's a motor and takes a startup surge load.
Then you just need to pick enough batteries to to run 880watts for your specified period of time.
Is that what the motor is rated at or have you ammetered it out and find it's running load? Running load is probably a bit less than rated. But you never know.
If your going to keep the batteries in the house, you'd need nice sealed batteries, like Optima's. The biggest deep cycle (blue top) optima they make is 75 amp-hours
(D31).
Meaning, it'll run 75amp load for 1 hour at 12v.That's 900 watts for 1 hour. FOr your situation, inverters are usually only 80% efficient at converting DC to AC power. So your actually wattage for an hour is 720. So you'd probably need 2 Optima D31's to really run your motor for an hour or slightly more.
Then your going to have to charge and keep charged those batteries, so you can either get an inverter with a built in charger. Or have a separate battery charger and keep them topped off at least once a month.
In all your costs involved would be something like:
2 Optima D31's (approx $200/each): $400
1000watt inverter : $120
or 1000watter inverter/10amp charger: $200
misc 8 gauge wiring : $20
So your in for $520 at a minimum and possibly more if you don't already have some other means to charge batteries and alot more if you want to run it for more than an hour (you'd need 2 batt's for every hour of operation, roughly).
I supposed you could disassemble the fan motor unit, because it'll have a giant AC to DC converter built into it (most all small motors run on DC anyway), if you wired the motor direct to the battery, you could not lose the 20% both ways and lose the cost of the inverter, so effectively a 40% gain on the system. But then you'd have to wire in a switch to be able to run it on normal AC.
My advice, buy a small gas Generator, far more useful for other things and less maintenance.
