, my 2 group 27 house batteries will run the unit on the
inverter for about one and a half hours.

considering that 2 group 27's will put out about 100 amps in an hour and a
half, or about 1,200 watts or about 3,600 btu's, you a/c unit ain't putting
out but about 1,000 btu's per hour of cooling.

not a hell of a lot.