Interesting I started looking at them, just browsing, but gotta get back to looking, so far I have only come across larger units that are mostly 8000 btu, I found one that was 7000, but cannot remember where, I have always used a simple 5000 window unit, and they are great, my advice on them is get the cheaper one that has manual controls, because the humidity will eventually mess up the electronics for turning on/off and temp control, then the remotes go bad, and unless you find a universal remote, can find on amazon for most, the original replacements are almost as much as unit, combined exp. of using them in various trailer builds and my house in Florida, I know this is a fact.
The Reason I am looking at portables is I can swap between van and trailer as needed without much fuss, just have separate exhaust in each camper.
Also if you are going to run off gernerator think about btu size, I like 5000 because my honda 3000 will run one in extreme heat for 21 plus hours, if you have a smaller gen, you are gonna use more fuel and will be louder all the time, the 3000 barely changes speed except for start up of a 5000. so thats the draw back so far on portables unless i can find a 5000, which maybe too small for a van with heat load of sun?
Sorry for long reply but just throwin it out there, I always try and think of all aspects,