· Michael Blair
Tankless water heaters last roughly twice as long as tank units and never run out of hot water. Both claims are true. What the pitch leaves out is that in moderately hard Middle Tennessee water, the maintenance a tankless unit needs to reach that lifespan is not optional, and the installation is rarely a straight swap.
What the swap actually involves
A tankless unit is not a like-for-like replacement. Gas models typically need a larger gas line than a tank heater was fed with, because they fire at a far higher rate on demand. They need their own venting, usually stainless or PVC depending on the unit, and they need a condensate drain.
That is why quotes vary so widely. A house where the gas line, the vent path and a drain are all easy is a straightforward job. A house where the heater sits in a closet in the middle of the floor plan is not, and the difference is most of the price gap.
Where hard water changes the answer
A tank heater tolerates scale badly but forgivingly. Sediment settles at the bottom, costs you efficiency, and eventually the tank fails. A tankless unit scales inside a narrow heat exchanger, where the same deposit restricts flow and triggers error codes long before it destroys anything.
The fix is a descaling flush, roughly annually here, using a pump and a vinegar or commercial solution through service valves. If those isolation valves were not installed, the flush becomes a much bigger job. Insist on them at installation.
Which one suits which house
Tankless makes sense in a household that genuinely runs out of hot water, in a house where floor space is worth money, or where you intend to stay long enough to see the longer life. It also suits a home already committed to annual maintenance.
A tank heater is the better answer for a straightforward replacement in a house you may sell within a decade, for a household whose hot water demand is comfortably met, and for anyone honest with themselves about not booking an annual service.
The softener question
A softener extends the life of either type and roughly doubles the interval between tankless descales. On a tankless installation in Middle Tennessee it is worth pricing at the same time, because the two decisions interact.
It is not a requirement. Plenty of tankless units run here without one and reach their expected life on annual flushing alone. It is a trade between one larger up-front cost and a maintenance habit you have to actually keep.