Dear M.J. Trust the T-M1 235,000btu gas tankless heater. I've sold & installed them for exactly your application. I have a T-M1 installed for a huge Jacuzzi type bathtub, which is fed with it's own 3/4" line. The owner can't overpower it unless she runs hot water somewhere else at the same time. I also have a similar (smaller)165,000btu unit in a commercial laundry. This unit produces 145 degree water at 240 gallons per hour, 18 hours per day. And has done this for six years, even if you have a family of six, this is more hot water than you will use in two, three, or four lifetimes. Besides, I give a five year warranty on the heat exchanger. Storage tank-type heat exchangers can be used in conjunction with the T-M1, to give higher flows. Many options exist for delivering lots if hot water. If you have more concerns or questions regarding tankless water heaters, please call me at 800 851 9891. Regards, Brian Wood.