I will be installing solar within the next month and will have a realistic usage as I intend to monitor every device one by one over a period of time. I will be sure to report back so other Challenger owner's benefit from my tinkering.
If you want to monitor device by device over a period of time for a realistic calculation, this is a inexpensive meter
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Best of luck boondocking and let us know how your travels go. Are you on RVillage too? While this is a great site for problem solving, RVillage is great site for staying connected.