I am thinking about purchasing two portable air conditioners. My condominium is 960 square feet, so each level is about 415 square foot. This is minus the stair case. I would like one for the upstairs and one for the downstairs. I would like to eventually do away with central a/c. I live in Mesa, Az. where temperatures in the summer can reach 112 and higher. Does anyone have any experience with portable a/c's? The cost, the reliability, any information will help. Also, as far as the operating cost on the electric bill. Central air is very expensive and can run over $200/mos if not more in Az.