Yeah, backup power for your two main pumps is gonna be something BIG AND UGLY. Figure a good 2-3kW capacity for two 1/2hp pumps to allow for surge current, about 1.2/1.5kW for running current. And your inverter is gonna need to be something you can store in a plastic bin or mount to the wall so water can't fry it.
The yellow belly special for the inverter is gonna be around $1100.
http://www.aliexpress.com/item/DC48...2317290406.html?spm=2114.40010508.4.77.EFMTiI
Figure that cost, up to 1.5/2 times more for the batteries.
http://bigtimebattery.com/store/t125_golf_cart_battery.html
So, about $2000-$3000
That sort of thing you could probably get hooked up without too much trouble. Just need to build a battery box with a hydrogen vent so no earth shattering kabooms.
Which should keep the fire marshal/insurance guys happy.
On the somewhat more pricey end, inverters here.
http://www.wholesalesolar.com/power-inverters
Magnum Energy ones aren't too terrible, even if their production and engineering staff are a bunch of screwballs even on a good day. Still, if it fries after some abuse, you only have to ship it to Everett, Wa, and I think they have under 7 day turn around time. Assuming they don't just swap it out.
Batteries plus inverter carts here.
http://www.wholesalesolar.com/back-up-power
Just plain deep cycle batteries, you can usually get Trojan 125s anywhere that services those robotic looking Genie Lifts, or that does electric golf carts, etc. The other issue is figuring out how much power outage time there might be, and sizing the battery bank accordingly. Wouldn't bother with anything cheaper than trojans, they're pretty much industry standard, and don't give you any unfortunate excitement.