Having endless hot water isn't the only advantage to having a tankless. Not paying to constantly have hot water in the tank while you are gone is another advantage. Sure you can shut off the gas, but this is very annoying to do every day. Not paying to heat water when no one is there (like during that day at work, etc) helps the payback but it really depends on what your current gas rate is.
By the way, what is "HWH"? I'm guessing it stands for hot water heater, but if the water is already hot, why do you need to heat it?
Engineer I first worked for used to gripe about that so all of us junior engineers at the time would make sure to put that on every spec
This thread reminds me I need to service mine. Surprising how few people drain/service their water heaters. It's so simple and really extends the life of the unit.