What model? They vary a good bit depending on what they have. Some have stile heaters that come on sometimes and if they have the icemaker option there is usually some heating involved with those too.
If it's just a straight propane powered refer and the only 12vdc used is for the igniter and control board those are usually somewhere in the 250 milliamp range.
The installation manual says to run a 16 AWG wire behind a 6 amp fuse (2-way fridge). The equates to 72 watts max, probably much less than 72 watts. Even at 72 watts, it's probably insignificant when considering all the other 12v loads you have.
Yes, it is a "straight propane powered refer and the only 12vdc used is for the igniter and control board". So the 250 milliamps its what i can expect.
I am having 2 Group 27 or Group 29 Interstate batteries put on the trailer.
We mainly dry camp for a week at a time. I am trying to sort out if a generator is in my future.
Welcome to the forum. I had that exact same trailer (2014 198RD) before my current one and we really enjoyed it. The fridge will use a small amount of 12V power to control its circuitry but the cooling is done by burning propane. The fridge runs very efficiently on propane. The big 12V killer is the furnace - if you stay away from using it you could go a day or two on a standard group 24 12V battery. I swapped to LED lights and dual 6V deep cycle batteries on my 198RD and we camped 4 days on battery and propane without needing a recharge.
It's pretty easy to figure current usage if you know the current draw of an item. Draw can usually be found in the specs but is not the same as the fuse size for the item.
Let's assume the awning motor draws 10 amps. If you run the motor for an hour that would be 10 amp/hours. If you run it for 2 hours that would be (10 x 2) or 20 amp hours. If you run it for 1 minute that would be 10/60 amp hours. If you run it for 30 seconds that would be 10/120 amp hours. If you run it 20 times for 30 seconds each time that would be ((10/120) x 20) amp hours.
I would think you would definitely need a generator to dry camp for a week at a time. Between the Fridge, propane detector, water pump, lights and other parasitic loads, I found on our old 23b we had to run the generator every other day or so. this was with a group 31 battery. The new rig (27rls) was ordered with 2 6V interstates, so we'll see how that goes this summer, as we dry camp for 2 weeks at a time.