How much does a tankless water heater cost?
A tankless water heater costs $1,200 to $5,500 installed in 2026, and $300 to $700 to repair. What changes your price is below.
If yours is broken, most tankless water heater repairs run $300 to $700. A descaling flush, which fixes the most common problem, is $150 to $300. Igniters, sensors and thermistors are $150 to $450. A heat exchanger is the big one at $500 to $1,300, and at that price on an old unit, replacement starts to make sense.
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A fair price is $75 to $250.
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Middle of the range: $165
What you are paying for
How we calculate this
Prices are for the United States in 2026 from published cost guides, checked September 2026. This is an estimate, not a quote.
Cost by job
| Diagnosis and error code check | $75 to $250 |
|---|---|
| Descaling flush | $150 to $300 |
| Igniter or flame rod | $150 to $350 |
| Flow sensor | $150 to $400 |
| Thermistor or thermostat | $200 to $450 |
| Water valve or inlet filter | $150 to $350 |
| Control board | $300 to $700 |
| Venting or exhaust repair | $200 to $600 |
| Heat exchanger | $500 to $1,300 |
| Gas valve | $350 to $800 |
What to know before you book
| Scale is the usual cause | Most tankless calls trace back to mineral scale in the heat exchanger. Rinnai, Navien and Rheem all tell owners to flush yearly, and in hard water areas they mean it. A $150 to $300 flush prevents a $1,000 heat exchanger. |
|---|---|
| Your warranty may be void | Manufacturers can deny a heat exchanger claim if the unit was never flushed or was installed without a permit. Keep the flush receipts. |
| Read the error code | Tankless units show a code on the panel. E11 or 11 on a Rinnai is ignition failure; LC is scale; 12 is flame loss. Look it up before you call so you know whether it is a $200 fix or a $1,000 one. |
| Fewer techs know them | Not every plumber services tankless. The brand's website lists trained installers. An untrained plumber charges the same and guesses. |
| Repair or replace | Replace if the repair is over half the price of a new unit, or the unit is past 15 years. Tankless heaters last 20 years with flushing and 10 without. |
| Emergency | No hot water is not a night time emergency for most homes. Wait for the morning rate; the after hours fee is $100 to $350. |
Why it costs what it costs
A tankless heater is a small furnace with sensors, a control board and a heat exchanger the size of a shoebox. The parts cost more than tank heater parts, fewer plumbers carry them on the truck, and a lot of the labor is diagnosis. That is why a tankless repair averages $600 while a tank repair averages $400, and why the flush that keeps the exchanger clean is the best money you will spend on it.
Tankless water heater cost to buy and install
| Installed, all types | $1,200 to $5,500 in one July 2026 guide. Another puts it at $1,400 to $5,600. |
|---|---|
| Gas condensing whole home unit | About $3,100 installed on average. |
| Electric whole home unit | About $1,800 installed on average. |
| The unit alone | $450 to $4,000 according to Angi. It is only 30 to 50 percent of the total. |
| Swapping an old tankless for a new one | $1,000 to $3,500. The gas line, vent and wiring are already there. |
| Switching from a tank to gas tankless | $2,500 to $5,500. New venting and often a bigger gas line. |
| Switching from a tank to electric tankless | $1,400 to $4,500, plus $1,000 to $2,000 if the panel needs an upgrade. |
| A standard tank instead | $600 to $3,100 installed. |
| Yearly upkeep | $80 to $250 for a gas unit. |
Tankless units are 24 to 34 percent more efficient and last 20 years or more, against 8 to 15 for a tank. The payback on a gas tankless against a gas tank is long, about 7 to 12 years in one 2026 comparison. Check before you count on a federal tax credit: one July 2026 guide says it no longer applies to 2026 installs, while others still list $600.
Why this costs more in 2026
Tankless units are copper and steel and ship long distances, and the vent pipe is plastic.
Since the war with Iran began in late February 2026, oil has been the cost that moved. AAA put diesel above $6 a gallon for the first time on September 11, 2026, against about $3.70 a year before (CBS 8 reporting AAA). Trade groups saw it early: by March, construction input prices were up 4.8 percent in a year and diesel had its largest one month rise since 1990, at 37.8 percent (Roofing Contractor, April 2026). A price you were given in the spring may not hold. Ask for a fresh quote.
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Common questions
How much does it cost to repair a tankless water heater?
$300 to $700 for most repairs in 2026. A flush is $150 to $300; a heat exchanger is $500 to $1,300.
How often should a tankless water heater be flushed?
Once a year, or twice a year in hard water areas. It is the repair that prevents the others.
Should I repair or replace my tankless water heater?
Repair unless the quote is over half the price of a new unit or the heater is more than 15 years old.
Why is my tankless water heater showing an error code?
Codes point to ignition, flame loss, scale, or a sensor. Look up the code for your brand before calling; it tells you what the repair will roughly cost.
Does a plumber or an HVAC tech fix a tankless heater?
A plumber, ideally one trained by the brand. The gas and venting side overlaps with HVAC, but plumbers do most of the work.
Other jobs and rates
Compare prices
Related jobs people check next, with the usual 2026 price.
| Job | Usual price |
|---|---|
| Water heater replacement cost | $600 to $3,100 |
| Water heater repair cost | $150 to $1,017 |
| Home Depot water heater installation cost | $1,200 to $5,400 |
| Heat pump water heater cost | $1,800 to $6,500 |