We replaced our old natural gas, forced air furnace and old standard hot water heater about four years ago with a more efficient Rudd furnace and a Rinnai tankless hot water unit and are very happy with the change. Our utility bills have plummeted, and we have plenty of hot water (even with a houseful of company at the holidays). It does take a bit longer for the hot water to reach our second story master bath, but it did so with the old water heater as well -- the cool standing water in the pipes has to flush out regardless of the type of heater. Our new units were professionally installed. Note that the tankless unit did require three new water lines, plus the gas line, and a new vent through the roof. Be sure to choose a tankless unit (as well as a furnace) appropriate for the size of your house.

Hi Mark. We are debating the same for our new home that we're renovating. Did you end up installing this ? How did it work out ?

Mark, can you please share your experience, either post installation or even if you decided not to do it?