Although you do say you don't plan to spend summers in Phoenix, if you do spend good time in the SW deserts, you may want to consider a swamp cooler as your second - as it can run on 12v instead of requiring shore power. This will open you to significant boondocking possibilities.
I have 26 U with two A/C units and 50 Amp service. Unfortunately a lot the state parks in Fl only have 30 amp service. Oddly the camp areas for horses have 50 amp service. I have found the front A/C unit will cool the trailer well, but with both A/C units it will cool it faster in hot weather. i have bought 50 amp connector for hooking up to trailer and then use 15 foot 50 amp extension cord. This all you usually need instead of heavy cord that came with trailer. I just use 30 amp cord it that is all that is available at campsite or with generator. With 30 amp service I turn off rear A/C unit.
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