Water heater cost comparison
Compare what a heat pump, gas and electric resistance water heater cost to run in your state.
Heating 55 gallons a day costs about $168.54 a year with a heat pump water heater, $292.91 with a gas tank and $641.17 with an electric resistance tank at U.S. average prices (18.16¢/kWh, August 2026; gas $1.48/therm, 2025; EIA).
- Heat pump per year
- $168.54928 kWh
- Gas per year
- $292.91198 therms
- Electric resistance per year
- $641.173,531 kWh
Formula: heat = gallons/day × 8.24 lb/gal × temperature rise × 365; electricity kWh = heat ÷ (UEF × 3,412); gas therms = heat ÷ (UEF × 100,000). Energy cost only; excludes purchase, installation and maintenance.
Inputs used: hot water: 55 gal/day; rise: 67 °F; UEF: HP 3.5, electric 0.92, gas 0.56; electricity: 18.16¢/kWh; gas: $1.48/therm.
These are estimates, not financial advice.
Source: U.S. Energy Information Administration (Aug 2026). About our data
Natural gas: U.S. Energy Information Administration, residential annual average. Test constants and minimum ratings: U.S. Department of Energy (10 CFR 430).
Worked examples in three states
| State | Electricity | Gas | Heat pump/yr | Gas/yr | Electric/yr |
|---|---|---|---|---|---|
| Hawaii | 47.18¢/kWh | $5.71/therm | $437.86 | $1,130 | $1,666 |
| Alabama | 16.33¢/kWh | $1.70/therm | $151.55 | $336.45 | $576.56 |
| Nevada | 12.72¢/kWh | $1.26/therm | $118.05 | $249.37 | $449.10 |
How we calculate
heat (Btu/yr) = gallons/day × 8.24 lb/gal × 1.00 Btu/lb·°F × temperature rise × 365; kWh = heat ÷ (UEF × 3,412); therms = heat ÷ (UEF × 100,000). Constants follow the DOE rating test (10 CFR 430, Appendix E). Default gas and electric UEFs are the federal minimums for 50-gallon tanks; the heat pump UEF is an example value.
Frequently asked questions
Which water heater is cheapest to run?
With the default ratings, a heat pump water heater uses about 26% of the electricity of an electric resistance tank. At U.S. average prices it costs about $168.54 a year versus $292.91 for a gas tank and $641.17 for electric resistance.
What is UEF?
Uniform Energy Factor: the federal rating of how much of the energy a water heater uses ends up as hot water, measured in a standard test. Higher is better; heat pump models exceed 1 because they move heat from the air.
How much hot water does a household use?
The federal rating test uses 55 gallons a day for a “medium” household. Larger households use more; the calculator lets you change it.
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