a Dometic 13,500 btu uses 15.3 amp. and the 15,000 runs up to 15.98 amp. not much difference for 1500btu more. The Dometic Penguin heat pump 13,500btu draws less, 12.7amp The Penguin 15,000btu A/C only (not heat pump) draws 12.9.amp
You can run two roof airs on 4kw, you can't start two air cond at the same time and you don't want them to cycle on and off.set the stat to the coldest. I would not use anything else that has a big demand, like coffee, pot microwave, welder,or table saw. We ran two coleman air on a 4kw for years with no problem. 30' Super Chief.Bago