1. His RV is from 1999. Insulation back then was a joke.
2. Rule of thumb in the RV business is: anything above 32' should have 2 AC roof units.
3. 5000 BTU in a 40' trailer / RV is not enough in Florida, for at least 6 months out of the year. Unless you call temps in the 80s comfortable.
4. Scaling an AC depends on MANY factors, like location, insulation, color of exterior, age and condition of RV, humidity, altitude. A general claim like OP or you make is senseless, and doesn't work globally. Getting an AC / solar / battery system running in Canada is a totally different story than down South!
Here's a new update, as we're in the total summer heat here, even in canada...
So on the solar news, yes it's true, my solar return is lower than in Florida, about 20% less than the panel rating. Which is fine, as long as you plan accordingly.
Regarding insulation, it's all pink insulation, walls, ceiling, and double plywood floor has 1.5 inches between as well. Not horrible, not great. The window frames are too hot to touch, no matter what you do with the coverings. It's really alot of heat transfer. That part is truly horrible and I wish I could change that alone.
So, it's hot for here, it's 90+ days, I have zero shade on purpose, and it's 78 at night. Day after Day after Day. So my cooling demands have changed as well. There's basically no cool down overnight, as I keep the inside at 72. The solar charge shuts off WAY before the AC now, so it runs on battery alone for the evening, and then less at night once the walls etc cool down in the dark. With that said, the AC load is consuming around 120ah out of the battery bank each night. Of course this regenerates in the morning easily when the sun is less hot and the unit is already cool from the darkness. Then shortly after sunrise, rinse and repeat etc. During the day I'm still charging and keeping up with the loads no problem, so not much to say about that.
Some factors that would crush this good progress: WORSE insulation, MORE heat, bad solar production, etc. For now, the setup is perfect for my needs.
Interesting driving fact.. I turn off the Heatpump AC when driving only. .. and the dash AC keeps the temps reasonable, so that also kills the DC load.. and ALWAYS tops off the batteries when we drive anywhere. The highest load in the unit is always the AC, so if it's off for any reason (think power management) then the recharge is plenty fast at 800~ watts. We do NOT have a charger that uses alternator power.
Plans: I'm going to add another 395w panel up top on a second charge controller. I have the space, it's not expensive for the panel (same as my 3rd one) and I already have the 40a Epever unit in a box from years ago. This will just crush some more load, and adding another 30% of charge capacity is all I think I'll ever need when travelling in more hot climates.
Review on the Senville 9000btu split AC 110v version: This thing is NOT working at all near it's full capacity. I have it set on 'COOL' function, temperature measured in the head unit (and not the hand held remote) and I set and forget. It has a turbo mode, and if I ever turn it on the watts usage will more than double... it's very strong, and I'm not using it any where near it's capacity to keep up with my cooling needs. I'm very pleased with it for my RV. I'll be doing a trailer rebuild next year and I'll use it again as well.