[bushpilot]

I've got 3 house batteries - 12v deep cycle giant bastards.
We never use our dc to ac inverter, so like bob ours runs the fridge, lighting, water heater (when on propane) and an outdoor electric cooler.

I can go a solid 24 hrs on the batteries (the outdoor cooler is the big consumer) - never tried to go longer....i run the gen at night to charge the batteries & run the air conditioning.

my roof top AC units consume anywhere from 11-15 amps (sometimes slightly higher if its really hot)....I can't find the spec not he 15k BTU unit but the 13.5 requires 1300+ watts (running, not startup).

assuming you'll have a heat strip int he ac unit you'll need at least 1800 watts for that....w/ a 20kw gen set I'm not sure you'll have enough room for all the batteries.