This may not apply to the OP, but here is what I do: I mostly use my TC in winter at ski area parking lots. My 18k btu propane furnace will draw my AGM battery down in about 24 hours. It takes about 6 hours with the camper plugged in to my Honda 2000i to fully charge the battery but only if I turn the propane heater off and switch to a 900w electric heater while the gen is running and I also have enough power to charge computer battery and run a ski boot drier.
If I try to run the propane furnace and try to charge a low batt. at the same time, the fan in the propane heater will draw down the battery almost as fast as it is being charged. If I used a Honda 1000 gen then I would not be able to charge the batt. and run an electric heater.