How long does a tankless water heater last?

Around 20 years on average: that is the product lifetime the U.S. Department of Energy (DOE) estimated for consumer gas-fired instantaneous water heaters in its 2024 rule (2024 rule, data 1974-2021, read 2026-10-29, national, n not published by the source). DOE identified tankless models as the majority of that category (2024 rule, data 1974-2021, read 2026-10-29, national).

Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026. Updated 2026-10-28

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We computed these shares from the public microdata of the 2020 Residential Energy Consumption Survey (RECS) of the U.S. Energy Information Administration (EIA). Of all US households, 6.5% had a main water heater in EIA's size category “Tankless or on-demand” (EIA RECS 2020, read 2026-10-29, n = 18,496, SE 0.2 points). For Florida households the share was 5.9% (EIA RECS 2020, read 2026-10-29, n = 655, SE 1.0 points). EIA imputed (filled in statistically) the water heater size for 21.4% of the US households counted and 18.5% of the Florida households counted. Each figure is a share of homes in 2020, never a water heater's age or how long a tankless unit lasts.

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By InstaBids editorial team with AI research agents. Sources read: 29 October 2026

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In our own counts, n is the number of surveyed households behind a share and SE is its standard error, a measure of sampling error, in percentage points.

How long it lasts, by source

Tankless water heaters, on ENERGY STAR's gas tankless water heater page: “Tankless water heaters have a life expectancy of 20 years, much longer than any conventional tank-type water heater.” (no issue date, read 2026-10-29, national, n not published by the source)
Gas-fired instantaneous vs gas-fired storage water heaters: in its 2024 rule, DOE compared the lifetimes it estimated, writing that “the average lifetime of a gas-fired instantaneous water heater is approximately 20 years, compared to approximately 14.5 years for GSWHs,” its short form for gas-fired storage water heaters (2024 rule, data 1974-2021, read 2026-10-29, national, n not published by the source).
Tankless vs traditional tank heaters, in a DOE Building America fact sheet: “their expected equipment life is longer – more than 20 years, compared with 10 to 15 years for traditional heaters.” (last update 8-18-2009, read 2026-10-29, national, n not published by the source)
Electric tankless units: no source on this page prints a lifetime for them. In its 2024 rule, DOE estimated an average product lifetime of around 20 years for gas-fired instantaneous water heaters only (2024 rule, data 1974-2021, read 2026-10-29, national, n not published by the source).
A warranty, not a lifespan: ENERGY STAR's criteria for the gas-fired instantaneous water heaters it lists call for “Warranty ≥ 6 years on heat exchanger and ≥ 5 years on parts” (no issue date, read 2026-10-29, national, n not published by the source).

DOE defined the term this way: “Product lifetime is the age at which an appliance is retired from service.” In its 2024 rule, DOE estimated its survival function from appliance ages in two surveys: “For this analysis, DOE relied on RECS 1990, 1993, 2001, 2005, 2009, 2015, and 2020.” and the American Housing Survey (AHS) “from 1974-2021” (2024 rule, data 1974-2021, read 2026-10-29, national).

Status of that rule: DOE's withdrawal notice states, “As of May 20, 2025, the final rule on energy conservation standards for gas-fired instantaneous water heaters, published in the Federal Register on December 26, 2024, at 89 FR 105188, and delayed at 90 FR 13054 (Mar. 20, 2025), is withdrawn.” (2025 rule, data years not published, read 2026-10-29, national). The notice withdraws the standards; it prints no new lifetime figure.

Type	Measure	Figure	Area	Data years	Source
Tankless water heaters	life expectancy (ENERGY STAR statement)	20 years	US	no issue date	ENERGY STAR, gas tankless water heaters page, read 2026-10-29, n not published by the source.
Consumer gas-fired instantaneous water heaters (mostly tankless models)	average product lifetime, around (DOE estimate)	20 years	US	1974-2021	U.S. DOE, 2024 gas-fired instantaneous water heater rule (withdrawn 2025), read 2026-10-29, n not published by the source.
Gas-fired storage (tank) water heaters	average lifetime, approximately (DOE estimate, same rule)	14.5 years	US	1974-2021	U.S. DOE, 2024 gas-fired instantaneous water heater rule (withdrawn 2025), read 2026-10-29, n not published by the source.
Tankless water heaters	expected equipment life (Building America fact sheet)	20 years (the source says “more than 20 years”)	US	last update 8-18-2009	U.S. DOE Building America, Tankless Water Heaters fact sheet, read 2026-10-29, n not published by the source.
Traditional (tank) water heaters	expected equipment life range (Building America fact sheet)	10–15 years (the source says “10 to 15 years”)	US	last update 8-18-2009	U.S. DOE Building America, Tankless Water Heaters fact sheet, read 2026-10-29, n not published by the source.
Gas-fired instantaneous water heaters that ENERGY STAR certifies	minimum warranty on the heat exchanger (a WARRANTY term, not a lifespan; parts: 5 years)	6 years	US	no issue date	ENERGY STAR, Water Heater Key Product Criteria, read 2026-10-29, n not published by the source.
Main water heater in EIA category “Tankless or on-demand” (share of US households in 2020; not a lifespan)	weighted share	6.5 percent of households	US	2020	U.S. EIA, 2020 Residential Energy Consumption Survey (RECS), public-use microdata v7, read 2026-10-29, n = 18496, SE 0.2 points.
Main water heater in EIA category “Tankless or on-demand” (share of Florida households in 2020; not a lifespan)	weighted share	5.9 percent of households	Florida	2020	U.S. EIA, 2020 Residential Energy Consumption Survey (RECS), public-use microdata v7, read 2026-10-29, n = 655, SE 1.0 points.

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When a tankless water heater nears these ages, you can describe the new unit once on InstaBids and contractors bid on it in writing.

Signs it is near the end

Sign or age	What the source says	Source
Visible corrosion	ENERGY STAR, in an article on water heaters in general: “Visible corrosion – Corrosion is a sign that the water heater is breaking down.” (article dated Feb 2, 2024, read 2026-10-29, national)	ENERGY STAR water heater replacement article (Feb 2, 2024), read 29 October 2026.
Water leaking	ENERGY STAR: “Water leaking – Leaks from any joints, seals, or seams of your hot water heater is usually an indication there is a problem (potentially caused by corrosion, as mentioned above).” (article dated Feb 2, 2024, read 2026-10-29, national)	ENERGY STAR water heater replacement article (Feb 2, 2024), read 29 October 2026.
Rust in the water	ENERGY STAR: “Rust in the water is usually a sign that the interior of the water heating system is corroding and breaking down.” (article dated Feb 2, 2024, read 2026-10-29, national)	ENERGY STAR water heater replacement article (Feb 2, 2024), read 29 October 2026.

If your tankless water heater shows corrosion, leaks or rust, you can post the job on InstaBids and compare written bids.

Questions

What is the life expectancy of a tankless water heater?

ENERGY STAR's gas tankless water heater page states: “Tankless water heaters have a life expectancy of 20 years, much longer than any conventional tank-type water heater.” (no issue date, read 2026-10-29, national, n not published by the source) The DOE Building America fact sheet gives the reason it saw: “Because tankless heaters do not store water, they are less subject to corrosion than tank-type heaters.” (last update 8-18-2009, read 2026-10-29, national, n not published by the source) In its 2024 rule, DOE estimated a survival function that “provides a lifetime range from minimum to maximum, as well as an average lifetime” (2024 rule, data 1974-2021, read 2026-10-29, national).

Source: ENERGY STAR gas tankless water heater page, read 29 October 2026.
Source: DOE Building America tankless fact sheet (2009), read 29 October 2026.
Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026.

How long does a gas tankless water heater last?

In its 2024 rule, DOE estimated an average product lifetime of around 20 years for consumer gas-fired instantaneous water heaters (2024 rule, data 1974-2021, read 2026-10-29, national, n not published by the source), and wrote that “gas-fired instantaneous water heaters can have longer lifetimes than gas-fired storage water heaters” (2024 rule, data 1974-2021, read 2026-10-29, national). DOE withdrew that rule as of May 20, 2025 (2025 rule, data years not published, read 2026-10-29, national). ENERGY STAR's criteria for the gas-fired instantaneous units it lists set a warranty of “≥ 6 years on heat exchanger and ≥ 5 years on parts” (no issue date, read 2026-10-29, national, n not published by the source), a warranty term and not a lifespan.

Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026.
Source: DOE 2025 withdrawal of the gas-fired instantaneous rule, read 29 October 2026.
Source: ENERGY STAR water heater key product criteria, read 29 October 2026.

Does a tankless water heater need to be flushed?

The DOE Building America fact sheet says: “When operated at the higher temperature settings and the water has a high mineral content, scaling of the low-mass heat exchanger is likely. The heating coils should be flushed with a descaling solution.” It adds: “Refer to the owner's manual for specific maintenance requirements.” (last update 8-18-2009, read 2026-10-29, national) In its 2024 rule, DOE estimated maintenance for “condensate withdrawal and deliming of the heat exchanger” on higher efficiency models (2024 rule, data years not published, read 2026-10-29, national). ENERGY STAR writes: “These gas condensing tankless water heaters, like gas condensing furnaces, require venting through a vertical PVC pipe and a condensate drain.” (no issue date, read 2026-10-29, national)

Source: DOE Building America tankless fact sheet (2009), read 29 October 2026.
Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026.
Source: ENERGY STAR gas tankless how-it-works page, read 29 October 2026.

Do tankless water heaters need to be replaced?

In its 2024 rule, DOE estimated an average product lifetime of around 20 years for consumer gas-fired instantaneous water heaters (2024 rule, data 1974-2021, read 2026-10-29, national, n not published by the source). ENERGY STAR also notes, about water heaters in general: “Sometimes water heaters can appear to be working fine and then fail without warning.” (article dated Feb 2, 2024, read 2026-10-29, national)

Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026.
Source: ENERGY STAR water heater replacement article (Feb 2, 2024), read 29 October 2026.

Should you repair or replace a tankless water heater?

In its 2024 rule, DOE estimated repair costs for higher efficiency models tied to the “burner and blower assembly” (2024 rule, data years not published, read 2026-10-29, national).

Source: DOE 2024 gas-fired instantaneous water heater rule (withdrawn in 2025), read 29 October 2026.

For flushing a tankless water heater or putting in a new one, you can post the job on InstaBids and see written bids.

Tankless water heaters with hard water, in climates that are warm year round and in Florida

The U.S. Geological Survey (USGS) says: “Water hardness varies throughout the United States.” (page dated August 24, 2026, read 2026-10-29, national) It adds: “When hard water is heated, such as in a home water heater, solid deposits of calcium carbonate can form.” and “This scale can reduce the life of equipment” (page dated August 24, 2026, read 2026-10-29, national). For tankless units, the DOE Building America fact sheet ties scaling of the heat exchanger to water with “a high mineral content” (last update 8-18-2009, read 2026-10-29, national).

On placement, the same fact sheet says: “Tankless units are typically installed on the interior, but in climates that are warm year round, exterior installation is possible to minimize the required interior mechanical space.” (last update 8-18-2009, read 2026-10-29, climates that are warm year round)

Our own weighted shares from EIA's public microdata: in Florida, 5.9% of households had a main water heater in EIA's category “Tankless or on-demand” in 2020 (EIA RECS 2020, read 2026-10-29, n = 655, SE 1.0 points). Across all US households the share was 6.5% (EIA RECS 2020, read 2026-10-29, n = 18,496, SE 0.2 points).

If your home has hard water or a warm climate, you can describe the tankless water heater job on InstaBids and contractors bid in writing.

More about tankless water heaters

What adding or replacing a water heater costs, with its own sources, is on our national cost page: How much does water heater replacement cost?

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Sources for the figures on this page

U.S. Department of Energy, Energy Conservation Standards for Consumer Gas-fired Instantaneous Water Heaters, final rule, 89 FR 105188 (December 26, 2024), section IV.F.6 Product Lifetime, p. 105230, read 29 October 2026. U.S. government work, public domain.
U.S. Energy Information Administration, 2020 Residential Energy Consumption Survey (RECS), public-use microdata file v7, read 29 October 2026. U.S. government work, public domain; EIA credited as the source. Microdata file: recs2020_public_v7.csv.
ENERGY STAR (U.S. EPA / DOE), gas tankless water heaters page, read 29 October 2026. U.S. government work, public domain.
Consortium for Advanced Residential Buildings, Tankless Water Heaters, U.S. Department of Energy Building America fact sheet (last update 8-18-2009), read 29 October 2026. U.S. government work, public domain.
ENERGY STAR (U.S. EPA / DOE), Water Heater Key Product Criteria, read 29 October 2026. U.S. government work, public domain.
U.S. Department of Energy, Energy Conservation Standards for Consumer Gas-Fired Instantaneous Water Heaters, final rule; withdrawal, 90 FR 21390 (May 20, 2025), read 29 October 2026. U.S. government work, public domain.
ENERGY STAR (U.S. EPA / DOE), When Should You Replace Your Water Heater? (article dated Feb 2, 2024), read 29 October 2026. U.S. government work, public domain.
ENERGY STAR (U.S. EPA / DOE), How It Works: Whole-Home Gas Tankless Water Heaters, read 29 October 2026. U.S. government work, public domain.
U.S. Geological Survey, Water Science School, Hardness of Water (page dated August 24, 2026), read 29 October 2026. U.S. government work, public domain.

Method: our own shares, such as the 6.5% of US households whose main water heater was in EIA's category “Tankless or on-demand” (EIA RECS 2020, read 2026-10-29, n = 18,496, SE 0.2 points), are weighted with EIA's survey weights and carry standard errors from its replicate weights; every other figure is quoted from the source named beside it.