The Ruud and Amana were replacements after 22yr OEM units; a little costly but ROI is within sight now. I installed a tankless unit (saw it on ‘This Old House’ TV show) in my Family Farm Business Office 22yrs ago, and it still works. I’d never get a WH tank installed ever again.
I installed a Rinnai two years ago and our family loves it. Two people can shower at once, in separate showers of course, so there is no problem with demand. We had an 8 year old electric tank water heater and my electric bill has declined sharply and my gas bill didn’t go up that much. I installed a 97% efficient modulating York furnace a year before the tankless water heater. The next project will be a two stage heatpump, but I didn’t think about efficiency because I need a larger blower motor and bigger furnace body to achieve a high SEER to get a good rebate.