I have a customer on a remodel that wants to do away with their two existing natural gas water heaters that are past their prime and replace with one heater. There is just two of them, so my first thought was on demand but they have a large tub to fill and the plumber and rep tells me it wont keep up. We have looked into the heatpump water heater but dont have any experience with them to say they are the way to go. Solar does not seem to be worth upfront investment. We are looking for the most efficent with a reasonable payback. Does any one have any experience with heatpump or any other ideas. Thanks in advance.