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Whole-home tankless gas (replacing a tank). The full price list is below.
How we get this data$2,000–$5,600 to replace a tank with a whole-home tankless gas water heater, installed, and $3,500 is typical. Whole-home electric tankless runs $1,000–$4,500, and a point-of-use unit for one sink $400–$1,500. Most of the extra cost over a $2,000 gas tank is new venting and a bigger gas line.
Prices verified November 2026 · Cross-referenced against 36+ American pricing sources · See methodology
Whole-home tankless gas costs $2,000–$5,600 installed when it replaces a tank. The rows below show where that money goes and what it costs to run.
| Job | Low | Typical | High |
|---|---|---|---|
| Whole-home tankless gas (replacing a tank)installed | $2,000 | $3,500 | $5,600 |
| Whole-home tankless electricinstalled | $1,000 | $2,200 | $4,500 |
| Point-of-use electric tankless (one sink)installed | $400 | $750 | $1,500 |
| Gas line upsize (½ in to ¾ in)per job | $400 | $600 | $800 |
| New tankless venting (wall or roof)per job | $400 | $600 | $800 |
| Tankless flush and descaleper job | $100 | $200 | $350 |
| Tankless repairper job | $300 | $600 | $1,300 |
| Gas tank, 40–50 gal (for comparison)installed | $1,100 | $2,000 | $3,100 |
| Running cost per year: tankless gasper year | $130 | $185 | $280 |
| Running cost per year: gas tankper year | $190 | $275 | $425 |
US prices, November 2026. Low is a simple job in a low-cost area; high is a bigger job or a high-cost city.
Yes. The same job costs more where labor and rent cost more. Here's how water heater prices in the biggest US metros compare with the US typical of $1800.
Labor, rent and demand move every job on this page in the same direction. Open your city's guide for its full local price list.
Gas supply and venting. A whole-home unit burns far more gas at once than a tank, so many homes need the gas line upsized from ½ inch to ¾ inch ($400–$800). The old tank's flue can't be reused for most tankless units, so new venting goes through a wall or the roof ($400–$800).
Size. A unit is sized by gallons per minute at your coldest inlet water, not by tank size. Homes with two or three showers running at once need a bigger unit, which costs more to buy and to vent.
Over 10 years, a gas tank costs about $4,750 ($2,000 installed plus $275 a year), and tankless gas about $5,350 ($3,500 plus $185 a year), at US average gas prices, before yearly descaling. The fuel saving alone rarely pays back the higher price.
Tankless makes sense when you want endless hot water, need the floor space, or plan to stay long enough to get the longer life: tankless units often last 20 years or more, against 8–12 years for a tank.
Whole-home electric tankless costs $1,000–$4,500 installed. It needs very large circuits, so many homes need panel work, which is what pushes the top of that range. Running cost is about $605 a year at the US average electric rate.
A point-of-use unit under one sink costs $400–$1,500 installed. It's a fix for a far bathroom or kitchen that waits a long time for hot water, not a whole-home heater.
Tankless units need flushing to clear scale: about once a year, or every six months with hard water. A plumber charges $100–$350 a visit. Ask for isolation (service) valves at install so the flush is quick.
A tankless swap is gas, venting and often electrical work, so it needs a permit and licensed pros in most places.
Red flags in a quote: no gas line sizing check, reusing the old tank's metal flue for a condensing unit, no isolation valves for descaling, or a unit sized for summer rather than winter water.
Over 10 years, a typical whole-home gas tankless unit costs about $7,350 if a plumber descales it every year. Upkeep is easy to forget when you compare prices.
A gas tank over the same 10 years costs $2,000 to install plus $275 a year for gas. Tanks need a yearly flush too. With soft water, fewer visits are needed, and the upkeep line drops a lot. Some makers also allow you to descale it yourself with a pump kit; check the manual.
Two showers at the same time need about 5 gallons a minute. Here's how to check your own home with the Department of Energy's method.
Electric tankless costs less to install, $2,200 typical against $3,500 for gas. But it gives less hot water at once and costs more to run.
| Item | Gas tankless | Electric tankless |
|---|---|---|
| Installed price | $2,000–$5,600 | $1,000–$4,500 |
| Hot water at a 70°F rise | About 5 gallons a minute (typical) | About 2 gallons a minute (typical) |
| Running cost per year | $130–$280 | More than gas at US average rates |
| Venting | Needed. New venting costs $400–$800. | None |
| Supply work | Many homes need a bigger gas line: $400–$800 | Very large circuits; panel work in many homes |
| Hot water in a power cut | No; most need power for the fan and controls | No |
| Best fit | Whole homes with two or more showers | Small homes, one bathroom, or warm areas |
Whole-home electric units need very heavy circuits. Ask a licensed electrician to check your panel before you buy.
Tankless won't get hot water to your tap faster. The water still travels the same pipe from the heater to the tap. If you wait a long time now, ask about a recirculation pump, or a small unit under that sink ($400–$1,500).
It won't give endless hot water to every tap at once. It gives endless hot water up to its flow limit. Open more taps than it can handle, and the water cools.
Most gas units need power to run their fan and controls. In a power cut you get no hot water. Many standard gas tanks keep working.
A tap opened only a little may not switch the unit on. You may also get a short burst of cold water between uses.
A tankless quote with no flow rate is the first thing to question. Also watch for these.
Ask the plumber to write down the pipe size, the length of the run and how much gas the unit burns at full power (its BTU rating). If the line is too small, the unit can't reach full output. Upsizing costs $400–$800. Gas work needs a licensed pro and a permit in most places.
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For endless hot water, space or a long stay in the home, yes. On fuel savings alone it pays back slowly: about $90 a year less gas than a tank, against $1,500 more up front at typical prices.
Often. Whole-home units need much more gas at once than a tank, and many homes need the line upsized from ½ inch to ¾ inch for $400–$800.
About once a year, or every six months with hard water. A professional flush costs $100–$350.
Yes, if your panel can supply it. Whole-home electric units need heavy circuits and cost $1,000–$4,500 installed, more if the panel needs an upgrade.
Most tank-to-tankless jobs take half a day to a full day, longer if the gas line or venting needs a long new run.
Usually not. Most gas tankless units need power for the fan and controls, and electric units need power to heat. Many standard gas tanks still work in a power cut.
No federal credit. High-efficiency gas units could get up to $600 under the 25C credit, but it ended for units placed in service after December 31, 2025. Some gas utilities still pay rebates, so check yours.
Often 20 years or more, against 8–12 years for a tank. Regular descaling ($100–$350 a visit) helps it get there.
Add the flow of everything you run at once. One shower and one tap need about 3.25 gallons a minute. Two showers need about 5. Then check the unit gives that flow at your winter temperature rise. Our size calculator can help.
$400–$1,500 installed, and $750 is typical. It serves one sink, not the whole home.
Because it's more than a swap. Many homes need a bigger gas line ($400–$800), new venting ($400–$800), a condensate drain and a permit. The unit itself also costs more than a tank.