i have a 9000 btu haier portable ac that i use in my conversion van (casita has ac) and i find that if i am in the shade on a muggy hot 95 deg. day it works fine and brings it down to low 70's...... If the sun is shining in thru the windows
then not too good mid 80's.... what i did was put that silver bubble insulation in all the windows
while in direct sunlight and then it works fine. To me not as good as a window ac but definately better than no ac. I used it one night in a very muggy south carolina night and it froze me out where i had to raise the temp of the unit so it would shut off once in a while.
If you decide to get one be sure it's the newer models that have the self evaporator so that you do not have to empty the water bucket...... most can also be used as a simple de-humidfier also.