With the right adapters you can measure each component of the whole trailer minus AC with a Kill-A-Watt meter. Mine is 15A max so the 15kbtu AC pushes it over max.
Connect the meter to the trailer, turn on the fridge and take a reading, turn the fridge off and the water heater on, take a reading, etc... Do this with each component. Don't forget the lights. It's best to do this with a fully charged battery so not to skew the readings or exceed 15A.
2011 Ford F-150 EcoBoost SuperCab Max Tow, 2084# Payload, 11,300# Tow,
Timbrens
2013 KZ Durango 2857