I think you did mean "tankless" water heater, so here is a link to some information about them.

http://www.tanklesswaterheaterguide.com/


I would think that one would need to determine what one's hot water usage is and then purchase a unit that would be able to handle that usage.  I would recommend going somewhere that the units are sold and look carefully at the physical size of the unit.

In addition, they have both electric and gas models.  I would think that "flash" firing in a gas unit would require quite a bit of LPG, so ask questions as to the amount of gas used during a "normal" heating session.  I'd also ask the same question of an electric unit as well.

Terry

Funny that you should ask that question because I was thinking of posting it myself. Still livingin a S&B home, whenever I do things around the house I am now asking myself the question 'would I also be doing it this way in an RV'.
Well the other day my hot water heater finally gave out. Got a new one but while I was shopping for one, I looked and studied a little bit for a tankless water heater. Right away I wondered if they exist in an RV. Although they do consume a lot of energy to quickly heat up the water running through it, it would reduce, I would think a little bit of the weight of the RV wouldn't it? That could be a tradeoff...
Looking forward to hearing some of the replies....

I've looked at them with the idea of replacing the one in our rig, but ours currently runs on either electric or propane. The tankless waters only run on propane as far as I can tell and since we have to pay for propane but not electricity I'll leave it as it is until they make a unit that runs on both.

Several of the motorhomes we've looked at online have the Aqua-Hot system. Our current 5th wheel has a 12 gallon hot water heater. So far we've never run out of hot water for showers. Really like the tankless idea.

I think my brother might have one in his truck -- I'll check and pass on any helpful info I get.