Does the upgrade actually pay for itself?
Both sides are computed on identical household assumptions, so the difference between them is a real difference rather than an artefact of two different sets of guesses.
Our assumption: $150 a year, chosen for descaling a tankless unit; no source we found publishes a price for it. It applies to whichever upgrade you pick, so set it to what yours needs, or to zero.
The written price for swapping in the same kind of appliance you have now, usually a tank. Blank uses the estimate from published ranges.
The written price for the appliance you are considering, usually tankless, including any vent, gas or electrical work in it.
Payback — but read the note
98.4 years
$3,150 extra up front, $32 a year back.
That is longer than the 20 years the appliance is expected to last, so on these numbers it does not repay itself within its own life. Federal guidance puts a tankless life at more than 20 years; the commercial cost guide starts its range at 15. The verdict uses 20, which gives the upgrade the most time to repay, and 15 is shown beside it.
| Now | Considering | |
|---|---|---|
| Cost to run for a year | $474 | $292 |
| Installed cost | $2,325 | $5,475 |
| Added servicing | $0 | $150 |
Energy saving before servicing: $182 a year. After servicing: $32. Excluded from both columns: any rebate or tax credit, the value of never running out of hot water, and the possibility that fuel prices move relative to each other over the appliance’s life.
| Input | Value | Basis |
|---|---|---|
| Energy prices, Texas State average residential prices; your own bill may differ. | 19.42 dollars per thousand cubic feet | sourced |
| Daily hot water Our default, not a published figure. Federal guidance quoted on this page treats 41 gallons a day or less as low use and around 86 as high use. Enter your own. | 64 gal/day | assumed |
| Cold-water inlet temperature Our starting value, not a published figure; enter your own. | 55°F | assumed |
| Delivered hot-water temperature The setting we chose; enter yours. | 120°F | assumed |
| Efficiency ratings used The federal minimum uniform energy factor for each appliance class, as listed on the methodology page. A real appliance may beat its minimum, which would move both running costs. | 0.5 now, 0.81 considering | sourced |
| Added yearly servicing Our assumption: $150 a year, chosen for descaling a tankless unit; no source we checked publishes a price for it. It applies to whichever upgrade is chosen, so set it to what yours needs. | $150 | assumed |
| Installed cost, like-for-like replacement Built from the published installed-cost ranges for the same scope of work. | $2,325 | modelled |
| Installed cost, the upgrade Built from the published installed-cost ranges, plus the extra work selected. | $5,475 | modelled |
| Service life for the verdict The sources disagree: federal guidance says more than 20; the commercial guide starts at 15. The longer figure is used; the shorter one is a row in the sensitivity table. | 20 years | sourced |
| Left out on purpose Each would move the answer, and none can be known for your address from here. | Rebates, tax credits, future price changes | assumed |
| Change | Premium | Net saving a year | Payback | Net over its life |
|---|---|---|---|---|
| As entered | $3,150 | $32 | 98.4 years, past its life | −$2,510 |
| Yearly servicing set to zero | $3,150 | $182 | 17.3 years | $490 |
| Yearly servicing doubled to $300 | $3,150 | −$118 | No payback | −$5,510 |
| Daily use at the federal low-use figure of 41 gallons | $3,150 | −$34 | No payback | −$3,830 |
| Daily use at the federal high-use figure of 86 gallons | $3,150 | $94 | 33.5 years, past its life | −$1,270 |
| Installed costs at the ends of the published ranges that favour the upgrade | −$1,425 | $32 | Nothing to repay | $2,065 |
| Installed costs at the ends of the published ranges that work against it | $7,725 | $32 | 241.4 years, past its life | −$7,085 |
| Service life at the shorter published figure of 15 years | $3,150 | $32 | 98.4 years, past its life | −$2,670 |
Before entering written prices, use the equal-scope worksheet to resolve included, extra and unknown work. Then compare the complete installed premium; a missing line is not free. Compare equal-scope quotes and worked ownership cases.
This tool can tell you the answer is no
That sounds like a low bar. A calculator that replaces a zero or negative saving with a small positive number so the division still works prints a large but finite number of years, and a reader then sees a slow win where the model found no win at all.
Here, a net saving of zero or less returns “no payback” and no year figure.
There is a second, subtler honesty problem this page tries to avoid: a payback that arrives after the appliance is dead. If the arithmetic returns a number of years longer than the equipment’s own expected life, the tool still shows the number, but it flags it rather than presenting it as a win. Twenty-eight years of payback on an appliance expected to last twenty is not a slow success.
The percentage advantage shrinks as you use more hot water
Federal guidance states it plainly. For a household using 41 gallons of hot water a day or less, a demand heater is 24 to 34 percent more efficient than a storage tank. For a household using around 86 gallons a day, the advantage falls to 8 to 14 percent[1].
The same federal page notes that tankless units avoid the standby heat losses of a storage tank. It does not say how much of the percentage advantage that accounts for, or why the percentage falls as use rises, so this page does not either.
The premium is the appliance and the job around it
At the tool’s defaults the tankless band’s midpoint is $1,600 above the fifty-gallon tank’s, and a first-time vent run at $500–$1,500[2] and a larger gas supply at $350–$750[2] add another $1,550 at their midpoints. These are historical cost estimates from an archived copy of the cost guide dated August 8, 2025.
That is why the scope selector sits inside this tool rather than being assumed away. With the default extra work the payback is 98.4 years. Set the extra work to nothing and it falls to 50 years, still past the 20-year life used for the verdict. With nothing extra and servicing at zero it is 8.8 years. Set the scope to what your house will actually need.
On service life the sources genuinely disagree, so both are shown rather than one being picked silently. Federal guidance gives a tankless unit more than 20 years and a storage tank 10 to 15[1]; a commercial guide starts its tankless range at 15 and its tank range at 8[2]. The verdict uses the longer life, which gives the upgrade the most time to repay its premium; the shorter life is a row in the sensitivity table, and there it makes the answer worse.
One line in this model is not sourced at all: the yearly servicing figure. Its default is our own assumption, chosen for descaling a tankless unit, because no source consulted publishes a price for that. It applies to whichever upgrade you pick, so set it to what your candidate needs, or to zero, and watch the answer move.
Two worked examples, run through the same engine
Neither example below contains a figure typed by hand. Both are calculated with the same functions as the tool above, so they change when a source figure changes.
A gas tank swapped for gas tankless, at the tool’s defaults
A household in Texas drawing 64 gallons a day (the tool’s starting value, our assumption rather than a published figure), needing a first-time vent and a larger gas line, and paying $150 a year in added servicing. No quotes entered, so both installed figures are modelled.
- Running cost now $474 a year, after the change $292: an energy saving of $182.
- Less $150 of added yearly servicing leaves a net saving of $32.
- Installed $5,475 for the upgrade against $2,325 to replace like for like (both modelled from published ranges): a premium of $3,150.
- $3,150 divided by $32 a year is 98.4 years, which is longer than the 20-year life used for the verdict, so it does not repay itself in time.
Verdict: 98.4 years, past its life.
| Input | Value | Basis |
|---|---|---|
| Energy prices, Texas State average residential prices; your own bill may differ. | 19.42 dollars per thousand cubic feet | sourced |
| Daily hot water Our default, not a published figure. Federal guidance quoted on this page treats 41 gallons a day or less as low use and around 86 as high use. Enter your own. | 64 gal/day | assumed |
| Cold-water inlet temperature Our starting value, not a published figure; enter your own. | 55°F | assumed |
| Delivered hot-water temperature The setting we chose; enter yours. | 120°F | assumed |
| Efficiency ratings used The federal minimum uniform energy factor for each appliance class, as listed on the methodology page. A real appliance may beat its minimum, which would move both running costs. | 0.5 now, 0.81 considering | sourced |
| Added yearly servicing Our assumption: $150 a year, chosen for descaling a tankless unit; no source we checked publishes a price for it. It applies to whichever upgrade is chosen, so set it to what yours needs. | $150 | assumed |
| Installed cost, like-for-like replacement Built from the published installed-cost ranges for the same scope of work. | $2,325 | modelled |
| Installed cost, the upgrade Built from the published installed-cost ranges, plus the extra work selected. | $5,475 | modelled |
| Service life for the verdict The sources disagree: federal guidance says more than 20; the commercial guide starts at 15. The longer figure is used; the shorter one is a row in the sensitivity table. | 20 years | sourced |
| Left out on purpose Each would move the answer, and none can be known for your address from here. | Rebates, tax credits, future price changes | assumed |
| Change | Premium | Net saving a year | Payback | Net over its life |
|---|---|---|---|---|
| As entered | $3,150 | $32 | 98.4 years, past its life | −$2,510 |
| Yearly servicing set to zero | $3,150 | $182 | 17.3 years | $490 |
| Yearly servicing doubled to $300 | $3,150 | −$118 | No payback | −$5,510 |
| Daily use at the federal low-use figure of 41 gallons | $3,150 | −$34 | No payback | −$3,830 |
| Daily use at the federal high-use figure of 86 gallons | $3,150 | $94 | 33.5 years, past its life | −$1,270 |
| Installed costs at the ends of the published ranges that favour the upgrade | −$1,425 | $32 | Nothing to repay | $2,065 |
| Installed costs at the ends of the published ranges that work against it | $7,725 | $32 | 241.4 years, past its life | −$7,085 |
| Service life at the shorter published figure of 15 years | $3,150 | $32 | 98.4 years, past its life | −$2,670 |
A heavy-use household holding two low quotes
The same state and servicing, but drawing 86 gallons a day — the federal high-use figure — with an installer who can reuse the existing vent. Its tank quote is $825 and its tankless quote $1,525: both set to the bottom of the published installed-cost bands for that scope. That is an illustration, not a real quote.
- Running cost now $637 a year, after the change $393: an energy saving of $244.
- Less $150 of added yearly servicing leaves a net saving of $94.
- Installed $1,525 for the upgrade against $825 to replace like for like (both from the quotes): a premium of $700.
- $700 divided by $94 a year is 7.4 years, inside the 20-year life used for the verdict, leaving $1,180 ahead by the end.
Verdict: 7.4 years.
| Input | Value | Basis |
|---|---|---|
| Energy prices, Texas State average residential prices; your own bill may differ. | 19.42 dollars per thousand cubic feet | sourced |
| Daily hot water The federal high-use figure quoted on this page. | 86 gal/day | sourced |
| Cold-water inlet temperature Our starting value, not a published figure; enter your own. | 55°F | assumed |
| Delivered hot-water temperature The setting we chose; enter yours. | 120°F | assumed |
| Efficiency ratings used The federal minimum uniform energy factor for each appliance class, as listed on the methodology page. A real appliance may beat its minimum, which would move both running costs. | 0.5 now, 0.81 considering | sourced |
| Added yearly servicing Our assumption: $150 a year, chosen for descaling a tankless unit; no source we checked publishes a price for it. It applies to whichever upgrade is chosen, so set it to what yours needs. | $150 | assumed |
| Installed cost, like-for-like replacement Set to the bottom of the published bands for this scope — an illustration, not a quote. | $825 | modelled (band low) |
| Installed cost, the upgrade Set to the bottom of the published bands for this scope — an illustration, not a quote. | $1,525 | modelled (band low) |
| Service life for the verdict The sources disagree: federal guidance says more than 20; the commercial guide starts at 15. The longer figure is used; the shorter one is a row in the sensitivity table. | 20 years | sourced |
| Left out on purpose Each would move the answer, and none can be known for your address from here. | Rebates, tax credits, future price changes | assumed |
| Change | Premium | Net saving a year | Payback | Net over its life |
|---|---|---|---|---|
| As entered | $700 | $94 | 7.4 years | $1,180 |
| Yearly servicing set to zero | $700 | $244 | 2.9 years | $4,180 |
| Yearly servicing doubled to $300 | $700 | −$56 | No payback | −$1,820 |
| Daily use at the federal low-use figure of 41 gallons | $700 | −$34 | No payback | −$1,380 |
| Service life at the shorter published figure of 15 years | $700 | $94 | 7.4 years | $710 |
Read the sensitivity rows before the headline. In the first example, 2 of the 7 changes turn the answer into a payback within the appliance's life (yearly servicing set to zero gives 17.3 years; installed costs at the ends of the published ranges that favour the upgrade gives nothing to repay), and 2 more change the answer without changing that (yearly servicing doubled to $300 gives no payback; daily use at the federal low-use figure of 41 gallons gives no payback). In the second, 2 of the 4 changes stop the upgrade repaying (yearly servicing doubled to $300 gives no payback; daily use at the federal low-use figure of 41 gallons gives no payback). A verdict that turns over when one line moves is a verdict about that line, which is why the tool asks for your own quotes and your own servicing figure rather than trusting ours.
Questions people actually ask
Is a tankless water heater worth it?
Sometimes, and the honest answer depends on numbers this page asks you for. The federal efficiency advantage is 24 to 34 percent for a household drawing 41 gallons a day or less, but only 8 to 14 percent for one drawing around 86. The heavier your use, the smaller the percentage advantage. The tool itself does not apply these percentages; it divides by the federal minimum efficiency of each appliance class.
How long does a tankless water heater take to pay for itself?
Whatever the arithmetic says, including never. This tool returns the number of years only when the annual saving after servicing is genuinely positive and the upfront premium is genuinely greater than zero. When it is not, it says there is no payback and shows no year figure at all.
Why does the vent line matter so much to payback?
Because it can be larger than several years of savings. A first-time vent run costs 500 to 1500 dollars and a larger gas supply line another 350 to 750, in an archived copy of the cost guide dated August 8, 2025. An upgrade that saves $100 a year (an illustrative figure) needs between 8.5 and 22.5 years just to clear those two lines, before the appliance premium is touched.
How long do these appliances actually last?
The sources disagree and this page shows both. Federal guidance says a tankless unit lasts more than 20 years and a storage tank 10 to 15; a commercial cost guide starts its tankless range at 15 years and its tank range at 8. The verdict uses the longer figure, which gives the upgrade the most time to repay its premium. The shorter figure is a row in the sensitivity table, and there it makes the answer worse.
Sources for the numbers above
- U.S. Department of Energy, Energy Saver (archived) — Archived source dated June 30, 2026: https://web.archive.org/web/20260630022620/https://www.energy.gov/energysaver/tankless-or-demand-type-water-heaters (checked 2026-08-06; re-checked 2026-10-01)
- HomeGuide — Historical cost estimate — archived source dated August 8, 2025: https://web.archive.org/web/20250808205107/https://homeguide.com/costs/water-heater-installation-cost (checked 2026-08-06; re-checked 2026-10-05). The live page refused an automated check on 2026-10-05, so whether it still prints these figures is not known.