Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Annual water heating cost
$642.95
Monthly cost
$53.55
Daily cost
$1.762
Annual savings if you switch to a heat pump unit
$445.78
Hot water used per day (gal)
60
Heat delivered per day (BTU)
32526
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter people in the household.
- 2Enter hot water per person (gal/day).
- 3Enter incoming water temp (°F).
- 4Enter tank setpoint (°F).
- 5Enter heater type.
- 6Enter electricity rate ($/kWh).
- 7Enter gas rate ($/therm).
- 8Read your annual water heating cost on the right — it updates as you type.
- 9Hit Share to keep the scenario or send it to someone.
About this calculator
Water heating is typically the second-largest energy load in a home. Heat pump water heaters cut that cost by roughly two thirds versus electric resistance tanks.
Worked example
Using the values the calculator loads with:
Inputs
- People in the household: 3
- Hot water per person: 20 gal/day
- Incoming water temp: 55 °F
- Tank setpoint: 120 °F
- Heater type: Electric tank (EF 0.92)
- Electricity rate: 0.17 $/kWh
- Gas rate: 1.4 $/therm
Results
- Annual water heating cost: $642.95
- Monthly cost: $53.55
- Daily cost: $1.762
- Annual savings if you switch to a heat pump unit: $445.78
- Hot water used per day (gal): 60
- Heat delivered per day (BTU): 32,526
What each field means
Inputs
- People in the household
- The people in the household used in the calculation. Starts at 3 so you have a working example on load. Accepted range: 1–12.
- Hot water per person (gal/day)
- The hot water per person used in the calculation, measured in gal/day. Starts at 20 gal/day so you have a working example on load. Accepted range: 5–60 gal/day.
- Incoming water temp (°F)
- The incoming water temp used in the calculation, measured in °F. Starts at 55 °F so you have a working example on load. Accepted range: 35–80 °F.
- Tank setpoint (°F)
- The tank setpoint used in the calculation, measured in °F. Starts at 120 °F so you have a working example on load. Accepted range: 90–150 °F.
- Heater type
- Pick the option that matches your situation — the maths changes per option. Choices: Electric tank (EF 0.92), Heat pump (EF 3.0), Gas tank (EF 0.62), Gas tankless (EF 0.82).
- Electricity rate ($/kWh)
- The electricity rate used in the calculation, measured in $/kWh. Starts at 0.17 $/kWh so you have a working example on load. Accepted range: 0.01–1 $/kWh.
- Gas rate ($/therm)
- The gas rate used in the calculation, measured in $/therm. Starts at 1.4 $/therm so you have a working example on load. Accepted range: 0.2–6 $/therm.
Results
- Annual water heating cost
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Monthly cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Daily cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Annual savings if you switch to a heat pump unit
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Hot water used per day (gal)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Heat delivered per day (BTU)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the water heater operating cost calculator work?
Water heating is typically the second-largest energy load in a home. Heat pump water heaters cut that cost by roughly two thirds versus electric resistance tanks. The underlying maths is: Energy = Gallons × 8.34 × ΔT ÷ efficiency; cost = energy × rate.
What do I need to enter?
7 values: people in the household, hot water per person, incoming water temp, tank setpoint, heater type, electricity rate, and gas rate. Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the annual water heating cost result mean?
It is returned as a money amount in US dollars and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Water Heater Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/water-heater-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/water-heater-cost" target="_blank" rel="noopener">Water Heater Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Water Heater Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/water-heater-cost) (2026).