I've had a Rheem tankless for 3 years and it has never performed well. Bath water would need to be turned on to get kitchen sink to get hot water. I've run the gamut with Rheem and their local choice for plumber (he wanted to sell me something different and wouldn't do any work on the Rheem). I've cleaned it, replaced what I could, and it still doesn't heat consistently.
I'm not new to tankless heaters. I ran Palomas in the 80s and 90s, no electricity and they worked great. I know the downsides.
Here's my question: I'd like to get a tankless without bells and whistles, preferably no electric parts, and can run a household with four teenagers. Our Rheem is outside and I would need the new one to be there also. Price is not the objective, though a good quality heater at a good price would be great! Any suggestions?