Tankless Water Heater Installation Cost Calculator
Tankless Water Heater Installation costs $3,675 to $5,575 for a typical 2 bathrooms job in 2026, against a national benchmark of $4,500. Labor runs 10.1 crew hours at $42.44 an hour. Enter a ZIP code to apply that area's measured wages for this work and its regional price level.
What makes up the price
Cost by size
National averages, before any local adjustment. Computed from the same model as the calculator above, so the two always agree.
| Bathrooms | GPM of flow | Typical | Range |
|---|---|---|---|
| 1 bathrooms | 4 | $3,725 | $3,050 to $4,625 |
| 2 bathrooms | 6 | $4,500 | $3,675 to $5,575 |
| 3 bathrooms | 9 | $5,650 | $4,625 to $7,000 |
The gas line is the hidden half of this quote
A storage tank burns about 40,000 BTU. A tankless unit sized for a two-bathroom house burns 150,000 to 199,000 — four or five times as much, because it heats water as fast as you can draw it rather than slowly over hours.
The half-inch line that fed the tank frequently cannot carry that. What is needed is a larger line run from the meter, and sometimes a larger meter from the utility.
That adds around 35% to the job, it is the single biggest variable, and it is not visible from a photograph of the old heater. Ask whether the gas line has been sized before accepting any quote, because a contractor who discovers it on installation day has a choice between a change order and an undersized install that never reaches its rated output.
The other thing that cannot be reused
The venting. A tankless unit cannot share a conventional flue: a non-condensing one exhausts too hot for plastic and needs category III stainless, and a condensing one vents in PVC straight out through a wall. Either way it is a new route, which is part of why this is a day's work rather than a morning's.
Condensing or not
| Condensing | Non-condensing | |
|---|---|---|
| Efficiency | 94–96% | 80–85% |
| Venting | PVC through a wall | Stainless steel |
| Unit price | Higher by ~$600 | Lower |
| Installed, 2 bathroom | ~$3,325 | ~$2,825 |
A condensing unit costs more to buy and less to vent, so the installed gap is smaller than the shelf prices suggest. Given the efficiency difference and that both last around twenty years, condensing is the right answer in almost every case where the exhaust can reach an exterior wall.
Does it pay for itself
Honestly, not quickly, and the page would be doing you no favors pretending otherwise.
A tankless unit uses roughly 25 to 30% less gas than a storage tank, because it is not keeping fifty gallons hot around the clock. For a typical US household that is $80 to $180 a year.
Against a job that costs around $1,800 more than replacing the tank with another tank, that is a payback of ten to twenty years — which is most or all of the unit's life.
The reasons that actually justify it
- It does not run out. This is the real reason people buy them and it is a genuine quality-of-life difference in a house where two showers compete.
- It lasts twice as long — around twenty years against eight to twelve for a tank.
- It is wall-mounted, which gives back the floor space a tank occupies. In a small utility room or a condo that matters.
- It cannot flood. There are no fifty gallons to escape when the bottom rusts through.
The energy saving is a real but secondary benefit. A salesperson leading with payback is quoting a number that does not survive checking.
Where it is the wrong answer
- As an emergency replacement. The gas line and venting work is exactly what cannot be done quickly, so an urgent tankless install is either rushed or quoted at a premium. With a tank already leaking, put a tank back.
- If you are moving within a few years. The premium is not recovered.
- In a house with a very low draw. One person in a one-bathroom home will never use enough hot water for the saving to matter.
- Where there is no exterior wall within reach for the vent.
Sizing, which is about flow rather than volume
A tank is sized in gallons. A tankless unit is sized in gallons per minute — how much hot water it can deliver at once — and it never runs out but it does run thin.
Roughly 3 GPM per bathroom covers a shower running with a faucet. The catch is incoming water temperature: a unit rated at 8 GPM is rated for a modest temperature rise, and in a northern winter where the mains water arrives at 40°F the same unit might deliver 5.
Size for the coldest month, not the average. This is the most common sizing error and it produces the complaint that the hot water goes lukewarm when it is cold out — which is precisely when it is noticed.
Maintenance that a tank does not need
A tankless unit has a narrow heat exchanger, and in hard water it scales up. Descaling it annually — circulating a vinegar or descaling solution through it for an hour — is what keeps it at its rated output and in its warranty.
That is only possible if service isolation valves were fitted at installation. They cost around $90 and they are the first thing left off a cheap quote. Without them, descaling means breaking into the pipework.
In hard water areas, ask about a softener or a scale filter as well. A tankless unit in untreated hard water is the one failure mode that turns a twenty-year appliance into a ten-year one.
Questions worth asking
- Has the gas line been sized, and does it need upsizing or a larger meter?
- Where does it vent, and is that run included?
- Are service isolation valves fitted?
- What GPM, at what temperature rise, and for which month?
- What does the warranty require in the way of annual service?
- Is a descaling visit included in the first year?
Common questions
How much does a tankless water heater cost installed?
Around $4,500 for a condensing unit in a two-bathroom home where the gas line needs upsizing, with most jobs falling between $3,675 and $5,575. If the gas line is already big enough it is closer to $3,325, and a non-condensing unit on an adequate line around $2,825.
Why does the gas line matter so much?
Because a tankless burner draws 150,000 to 199,000 BTU against about 40,000 for the tank it replaces, and the half-inch line that fed the tank often cannot carry that. A larger run from the meter — sometimes a larger meter — adds around 35% to the job. It is the single biggest variable and it is not visible from a photograph, so ask whether the line has been sized before accepting a quote.
Does a tankless water heater pay for itself?
Not quickly. It uses roughly 25 to 30% less gas, which for a typical household is $80 to $180 a year, against roughly $1,800 more than putting another tank in. That is a ten to twenty year payback on a unit that lasts about twenty. The reasons that justify it are not running out of hot water, double the lifespan, the floor space it gives back and the fact that it cannot flood — energy saving is a real but secondary benefit.
Should I get a condensing or non-condensing tankless?
Condensing in almost every case where the exhaust can reach an exterior wall. It is 94-96% efficient against 80-85%, and although the unit costs about $600 more it vents in PVC rather than stainless steel, so the installed gap is around $500 rather than the full difference in shelf price.
What size tankless water heater do I need?
Roughly 3 GPM per bathroom, which covers a shower running with a faucet — so about 6 GPM for two bathrooms and 9 for three. The important catch is incoming water temperature: a unit rated 8 GPM is rated at a modest temperature rise, and in a northern winter with 40°F mains water the same unit might deliver 5. Size for the coldest month, not the average.
Why does my tankless water heater go lukewarm in winter?
Almost always because it was sized for average conditions rather than the coldest month. Incoming water in winter can be 30 degrees colder than in summer, and the unit has to work that much harder for the same output — so a heater that is comfortable in September runs thin in January. It is a sizing error rather than a fault.
How long does a tankless water heater last?
Around twenty years, against eight to twelve for a storage tank — and that is one of the better arguments for it. The exception is hard water: a unit that is never descaled scales up its heat exchanger and can be finished in ten.
Does a tankless water heater need servicing?
Yes, annually in most water, and that is a real difference from a tank. Descaling means circulating a descaling solution through the heat exchanger for about an hour, which keeps it at its rated output and usually keeps the warranty valid. It is only practical if service isolation valves were fitted at installation — they cost about $90 and are the first thing a cheap quote leaves off.
Can a tankless water heater use the old flue?
No. A non-condensing unit exhausts too hot for plastic and needs category III stainless; a condensing one vents in PVC straight out through an exterior wall. Either way it is a new vent route, which is part of why this is a day of work rather than a morning.
Is tankless a good emergency replacement?
No. The gas line and venting work is exactly what cannot be done quickly, so an urgent tankless install is either rushed or priced at a premium. With a tank already leaking on the floor, put a tank back and plan the tankless properly if you still want one.
Where these numbers come from
Nothing here is copied from a contractor directory. Labor is priced from what the trades are actually paid, materials from published producer prices, and both are adjusted to your area using federal cost-of-living data.
- Plumbing, heating and air-conditioning contractors, United States: $42.44/hour, August 2026 (BLS CES CES2023822003)
- Condensing tankless water heater, base unit: $130.00 per heater (price recorded October 2026, not index-adjusted)
- Condensing tankless water heater, capacity: $191.00 per GPM of flow (price recorded October 2026, not index-adjusted)
- PVC concentric venting: $180.00 per heater (price recorded October 2026, not index-adjusted)
- Isolation valves, gas flex and water connections: $160.00 per heater (price recorded October 2026, not index-adjusted)