don't understand your question, but will try to explain what _may_ have been
your question.

An a/c unit will use about 1,400 watts electricity input to remove every 1,000
watts of heat.

1,000 watts = 3,012 btu's(according to the figures used by th HVAC industry [I
have family in the business long term])

A group 27 battery usually has aboout 100 amp-hour capacity, of which about 50%
is usuable. 2 grp 27's will give about a total of 100 amps before going dead,
as in unusable

100 amps at 12 volts = 1,200 watts = 3,600 btu's

across 1-1/2 hours that makes for about 2,400 btu's per hour INPUT (about 800
watts, about 65 amps).

Which makes for about 1,800 btu's of cooling.

sorry I used the 1,000 btu figure as I was just doing the numbers quickly in my
head.

btw, 1,800 btu's is about the cooling capacity of 12# of ice melting.

In other words, for drawing your 2 grp 27 batteries to their knees in an hour
and a half you will get about the cooling capacity of throwing about 18 pounds
of ice on your cabin sole.

, 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.