Historically these units have been problematic. They are also subject to variation in temperature of output based on water pressure and incoming water temperature. When training on them I was struck by the added complexity and the difficulties the manufacturers had in fixing malfunctions.
My thought would be to research any tankless water heater carefully focusing on owner complaints and repair when malfunctioning.
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