Let me put it this way, I have yet to see a PUP with a 13.5K or 15K air conditioner that isn't using a 20 amp receptacle inside the PUP. The PUP will have a 30 amp connection to shore power. That is sufficient to run everything simultaneously inside my PUP that draws electrical. The only exception to that is the furnace - I didn't turn it on when the A/C was on, even just for grins as there's no situation I can foresee where I would do that.
I had the A/C on, the 1,500 watt microwave, water pump, lights, refrigerator and all of the other parasitic draw devices running at the same time through my PDU/converter without problem.
In the winter, I run two electric heaters when on shore power to save on propane. I added another 120v circuit from the PDU just for the second heater as running both on the same circuit inside the PUP would indeed trip a 15 amp breaker.