In our last travel trailer I installed a Suburban IW60 on-demand tankless water heater. It was about the same size as the water heater I removed and weighed less (since it has no tank full of water). It was great! I like a long shower and I could take a shower while the wife was running hot water in the kitchen and I felt no change in water temperature. Link below to site.
https://www.pplmotorhomes.com/search...query=tankless