A lot of people want to use RV air conditioners for mobile applications because they don't want to cut a hole in the side of their trailer/truck. They are not a great option.
They are very expensive per BTU -- especially when you try to find one with a digital display. Dometic makes the original "BRISK" RV air conditioner which is digital. ***2016 models have a kit to change the thermostat to digital. No customers that we know have tried this yet. They have a sleeker looking one that is more expensive called the "Penguin" that's actually NOT as good for this application. So get the cheaper one, it's bigger on top which gives us more cooling area.
If you still want a roof mount AC consider this:
- They are annoying to set up, because you are working over your head and up in a hole and you can't see what you are doing, so it's hard to put our FIN sensor into place correctly. Worse yet, if the sensor falls out or the fins ice over, you won't know unless you look with a mirror and flashlight.
- Because of the very limited area that they are sucking and blowing out of (14x14) there is a BTU-transfer penalty of almost 30%. So you buy a 15,000 BTU unit, but it only puts out 10-11,000 BTU's of cold! Which makes them even more ridiculously overpriced.
- For all these reasons, even in vans, it's not so easy to get below 40F with an RV air conditioner. In smaller spaces it maybe possible, but overall the RV A/C is just more difficult to work with and less efficient than the window unit, which is super easy and good at what it does.
- We heard back from a guy who used a Dometic roof a/c for a year that he loved it! But he switched it out for a window a/c because of electric usage (the RV a/c took twice as much power to use.)