For me it comes down to cost and space.
I plan to mount the demand water heater outside either on the tongue box or on the front of the trailer with the controls aimed inwards so that they can be controlled from the shower.
I have no problem with the 4 gallon, six gallon or other units other that I would like to save a little weight
I may be wasting my money in this pursuit, but I think it has promise.
The water heater will be the only propane
consumer on my trailer (as planned).
I would go with an electric heater like an undercounter tank or demand, but I may not be where I have a hookup and it takes a while to heat the water.
I have filled in the front window on my Scamp
16' (originally side bath) and I am moving the bath to the front for more headroom.
Since this is a complete rebuild I have a clean slate, but not unlimited funds.
I have a friend who uses one of the inexpensive units on his toy hauler when competing in cooking contests and he has had good results and recommended it to me.
I don't think it is safe to place one in the confines of a tight trailer hence the outside mounting. I don't know if it can be set and forget therefore the consideration of mounting where the controls can be used from inside.
I say to each his own. I am not particularly concerned with the efficiency tank vs tankless since the overall cost is relatively small.
I do want to keep the electrical
demand below what a small inverter generator
4 gallons of water weight
32 lbs and the water heater may weigh another 30 (I don't know and I am just guessing here) for 60 lbs. (of course the demand heater weighs something too). Perhaps part of this weight
will go towards the generator
and a little fuel.