Brockpal: Bear in mind that while you may have existing 120V power wiring as Ron showed (not sure when "A/C Ready" became standard - it used to be an option) you definitely won't have any control wiring. You should discuss options with your installer - maybe unit mounted controls or some may even be available with a wireless remote now. Otherwise they are going to have to fish wiring under the vinyl headliner.
***Also don't put a jet engine on your roof. Several companies are FINALLY making strides to produce quieter rooftop air conditioners. They may not be easy to purchase or get installed in your neck of the woods but I would definitely look into the newer
Coleman Mach NDQ (non-ducted quiet) model (unfortunately they may only be available in 13.5K BTU...it won't dehumidify as well because it is a bit oversized for a 21 but it will still be quieter than the 11,000 BTU Dometic Penguin Escape uses) or you could call Advanced RV in Ohio and see if they will ship their
Houghton Belaire model to an installer near you. These are pricey but MUCH quieter than a standard Dometic or Coleman unit. They have a wireless remote standard. Check out this previous post of mine:
https://www.escapeforum.org/forums/f...tml#post338351