Updated 2026-09-04
The decision is not about hot water. Both deliver it. It is about whether the house has simultaneous demand or sequential demand, whether the gas line and the vent can serve a unit that draws four times the input, and what the customer is actually buying with the install premium.
Best overall
Tank, for most houses
It meets simultaneous demand at any flow, and the existing gas and vent usually serve it without a project.
Best value
Tank replacement
Half the install hours, no gas upsize, no new vent — the cheapest route to reliable hot water.
Best for endless supply
Gas tankless, sized at your rise
Sequential demand, a long service life and reclaimed floor space — provided the gas and vent are budgeted honestly.
| Factor | Tank | Tankless |
|---|---|---|
| Unit cost | $550–1,500 | $900–2,400 |
| Install hours | 2.5–5 | 6–18 |
| Gas input | ~40,000 BTU/h | 150,000–199,000 BTU/h |
| Usually needs a gas upsize | No | Often |
| Vent | Existing flue often reused | New PVC or stainless run |
| Hot water | Limited by tank and recovery | Continuous, limited by GPM |
| Simultaneous demand | Whole tank at once | Capped by flow at your rise |
| Standby loss | Yes, small on a modern unit | None |
| Service life | 10–12 years | ~20 years |
| Annual maintenance | Flush, anode check | Descale, filter clean |
| Footprint | A cupboard | A wall |
It delivers its whole capacity at once regardless of flow rate, which is what a house with two simultaneous showers actually needs. The replacement is a half-day, the parts are everywhere, and the existing gas and vent almost always serve it.
Against it: it heats water nobody used, it takes floor space, and it ends its life in about a decade — usually by leaking onto whatever is underneath it.
Endless hot water, twenty years of service life, no standby loss and a wall instead of a cupboard. On a house with sequential rather than simultaneous demand it simply never runs out.
Against it: the install premium is real and sometimes large, the flow cap is a hard limit at your climate's temperature rise, and descaling is not optional on hard water.
The rise is the whole specification
The energy saving is standby loss, and on a modern well-insulated tank that is a modest number. Against an install premium that routinely runs one to three thousand dollars, simple payback on energy alone frequently exceeds the unit's warranty period.
Sell the real advantages — endless supply, longer life, reclaimed space — and let the energy line be a bonus rather than the argument. A payback figure nobody measured is the claim that comes back in a review.
Before the model is chosen