Have you though about a evap cooler? If used correctly they can save you alot on your cooling. One of the few "old" green ideas that actually makes alot of sense power wise atleast.
We had a 2 Stage Mastercool with upduct discharge in our house in Lake Havasu City. It works well, and with the upducts it allowed you to run the system with the windows closed, and discharge the air through the attic which really kept the attic temperatures down.
The problem in Phoenix is the dew point is much higher during the Monsoon season, which greatly cuts down on the days you can run it. If you have a dew point over 40 degrees, it can really muck up your house, and worse
rust your guns! Evaporative coolers are the greatest destroyer of firearms in the state of Arizona. People run them when the dew point is too high trying to save money, and the indoor relative humidity can climb way too high, causing guns to easily rust, walls to sweat, and mold to form.
The other issue with them is constant service and leaking. All that controls the water input on even the most expensive units is a cheap little float switch, (valve), that can calcify and leak quickly. The pads require replacement every year, sometimes twice a year. In the Winter if it gets really cold, the water line on the roof can freeze and break causing even more problems. New home builders don't even offer them anymore. About the only place I could see one would be in the garage. In the Summer if you park 2 hot cars in a 2 car garage the temp can easily hit 130 inside your garage. An evap cooler would help get rid of that heat, and you could discharge it into your attic which would make your A/C run less. But I don't think I would install another one in my home unless energy cost went completely off the chart. Bill T.