Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Lower total cost option
Tankless
Tankless total cost
$7,200
Tank total cost (incl. replacements)
$9,000
Total cost difference
$1,800
Breakeven point
15.8
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter tankless unit + install ($).
- 2Enter tank unit + install ($).
- 3Enter tankless annual operating cost ($).
- 4Enter tank annual operating cost ($).
- 5Enter years to project.
- 6Enter tank lifespan (years).
- 7Read your lower total cost option on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Tankless water heaters cost significantly more to install than a standard tank but last nearly twice as long and use less energy by heating water only on demand instead of maintaining a hot reservoir. This calculator normalizes both options over a common horizon — accounting for the tank unit likely needing replacement mid-way through — to compare true lifetime cost.
Worked example
Using the values the calculator loads with:
Inputs
- Tankless unit + install: 3200 $
- Tank unit + install: 1300 $
- Tankless annual operating cost: 200 $
- Tank annual operating cost: 320 $
- Years to project: 20
- Tank lifespan (years): 10
Results
- Lower total cost option: Tankless
- Tankless total cost: $7,200
- Tank total cost (incl. replacements): $9,000
- Total cost difference: $1,800
- Breakeven point: 15.8
What each field means
Inputs
- Tankless unit + install ($)
- The tankless unit + install used in the calculation, measured in $. Starts at 3200 $ so you have a working example on load.
- Tank unit + install ($)
- The tank unit + install used in the calculation, measured in $. Starts at 1300 $ so you have a working example on load.
- Tankless annual operating cost ($)
- The tankless annual operating cost used in the calculation, measured in $. Starts at 200 $ so you have a working example on load.
- Tank annual operating cost ($)
- The tank annual operating cost used in the calculation, measured in $. Starts at 320 $ so you have a working example on load.
- Years to project
- The years to project used in the calculation. Starts at 20 so you have a working example on load. Accepted range: 1–30.
- Tank lifespan (years)
- The tank lifespan (years) used in the calculation. Starts at 10 so you have a working example on load. Accepted range: 1–20.
Results
- Lower total cost option
- Returned as a plain value and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Tankless total cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Tank total cost (incl. replacements)
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total cost difference
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Breakeven point
- Returned as a length of time. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why does the tank need replacing but not the tankless?
Standard tank heaters typically last 8-12 years while tankless units commonly last 18-20 years with maintenance, so over a long horizon you're often buying the tank unit twice.
Does tankless really save that much energy?
Tankless units avoid standby heat loss from keeping a full tank hot around the clock, typically cutting water heating energy use by 20-30% for a household with moderate usage.
Is tankless installation always more expensive?
Yes, especially if it requires upgraded gas lines or electrical service, which is why the upfront gap is wide even though the running cost favors tankless.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Tankless vs Tank Water Heater Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/tankless-vs-tank-water-heater-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/tankless-vs-tank-water-heater-cost" target="_blank" rel="noopener">Tankless vs Tank Water Heater Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Tankless vs Tank Water Heater Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/tankless-vs-tank-water-heater-cost) (2026).