I've heard of people using a Prius in a similar way. Great thing is, if the big Prius battery starts to run low, the gas engine automatically kicks in to charge the big battery.
Apparently you can run the AC as desired and use the Prius as an air conditioned tent, if you can sleep through the intermittent starting of the engine. Don't know if I could or not. There were some posts on the cheaprvliving web site by a woman who did a cross-country trip living in her Prius, for about 3 months. Too cramped for me, but it was definitely cheap1
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board