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Water Heater Energy Cost Calculator

Annual and monthly cost for the fuel you actually use, with the DOE draw pattern as the usage basis and cost per 1,000 gallons.

Inputs

How much hot water you use

The DOE test procedure defines four draw patterns with reference daily volumes (10 CFR 430 Subpart B Appendix E Table III). Pick the closest, or choose Custom and enter your own gallons.

Whole-house hot water use per day. A two-person household with daily showers commonly lands in the 40-60 gal/day range.

Temperatures

Year-round average groundwater temperature, not the coldest winter value.

The thermostat setting. The DOE test procedure solves at 125 F (Appendix E 2.4); a 50 F inlet with a 120 F tank is a 70 F rise.

Your water heater

Selects the right energy unit and price field. Only the price for the selected fuel is used.

Printed on the EnergyGuide label and the rating plate. Roughly: atmospheric gas storage 0.60-0.70, condensing gas 0.80-0.95, electric resistance storage 0.90-0.95, heat pump water heater 2.0-4.0. The UEF is not the steady-state efficiency; it is measured over a 24-hour draw pattern that includes standby loss.

Enter 0 to skip. A higher UEF gives the savings figure below.

Fuel prices - only the row for the fuel selected above is used

All-in cents per kWh from the bill, including supply and delivery.

Price per therm from the gas bill. Utilities often bill in CCF (100 ft3); at a heating value near 1,025 Btu/ft3, 1 CCF is about 1.025 therms.

Delivered price per gallon.

Roughly 91,500 Btu per gallon of liquid propane. Use the supplier's value if they publish one; the DOE test gas value in Appendix E is stated per cubic foot of vapour, not per gallon, so it is not used here.

Delivered price per gallon.

The DOE water heater test procedure lists fuel oil at 138,700 Btu/gal (10 CFR 430 Subpart B Appendix E).

Result

Annual operating cost
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Average monthly cost
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Annual site energy
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Cost per 1,000 gal of hot water
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Annual saving from the higher UEF
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Fuel-specific checks
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Where this stops applying
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Annual fuel in gallons (propane or oil)
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Annual energy in kWh (electric)
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Annual energy in therms (gas)
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Cost per gallon of hot water
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Cost per day
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Calculation details
Annual cost at the comparison UEF
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Daily hot water used
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Annual heat the water absorbs
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Average temperature rise
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Saving as a share of current cost
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Annual site energy before conversion
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Heat per billing unit of the selected fuel
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Billing units consumed per year
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What to check

  • UEF from the EnergyGuide label, and the current federal minimum for that class in 430.32(d)
  • The fuel price from a recent bill, in the unit the bill uses
  • Average groundwater temperature and the storage temperature

Standards referenced

  • DOE Uniform Energy Factor test procedure — 10 CFR Part 430, Subpart B, Appendix E · Uniform test method for measuring energy consumption of water heaters; UEF ratings on nameplates and EnergyGuide labels come from this procedure.
  • EIA residential electricity averages — EIA Electric Sales, Revenue, and Average Price / RECS (latest published year) · Reference data for default bill benchmarks only; your utility rate governs the actual bill.

Related calculators

Screening estimate only. The result panel lists the limits that apply to this calculation. Verify nameplate data, rates, groundwater temperatures and installer quotes before deciding, and have gas, venting and electrical installations checked against the local code by a licensed contractor.

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