Dating myself badly, the first tankless heaters in RVs were decades ago and were a disaster. Fortunately changing over to a standard DSI or DSI plus AC at that time was not difficult and lots of folks made the changes. Ultimately the biggest retailer of the tankless models sold them out at give away prices just to get rid of them. Later I had to work on models where the complaint was not enough hot water. The problem was they were so limited in pressure and incoming water temperature range they worked just fine if held within narrow parameters. More pressure or colder incoming water and adios warm shower. There are also parameters on the newer models, but with bigger heat sources.
While no longer involved in RV service, there were multiple complaints and it seems to me there still are regarding the current iterations thus my advice to research carefully and don’t rush into something that sounds ideal in concept, but works not so well in reality. Ask end-users who have them if they are satisfied (and don’t even get me started on the service aspect).
And yeah, the electric point of delivery models draw way too much power to be practical in RVs, as Don said. One of the horse trailer manufacturers tried using them which led to unhappy owners and work for me ripping them out and installing DSI models. Near 30 amp draw on a trailer with a 30 amp shoreline was just not a good idea. 🙂
Steve and Andra
2012 F350 6.2 gasser SRW LB
Fab Fours front and rear in case we run into a rhino
2019 Northstar Laredo SC