Water Heater Operating Cost Calculator
Estimate what it costs to heat your water each month and year. Electric and gas are calculated differently — this tool does not treat them as equivalent.
Estimated energy cost
Formula & what’s left out
Energy to heat water = gallons × 8.3454 lb/gal × (target − incoming) °F, in BTU, divided by your efficiency assumption. Electric results convert BTU→kWh; gas results convert BTU→therms. This estimates the energy to heat the water you use. It does not include standby (tank) losses, recirculation, or fixed meter charges, so a real bill is usually somewhat higher — especially for storage tanks.
What this calculator does
It estimates the energy cost of heating the hot water your household uses, based on how much water you heat, how far you raise its temperature, your utility rate, and an efficiency assumption you control.
The formula
Energy (BTU) = gallons × 8.3454 lb/gal × (target − incoming) °F. That heat is divided by your efficiency assumption to get input energy, then converted to kWh for electric (÷ 3,412) or therms for gas (÷ 100,000) and multiplied by your rate.
How to use it
- Choose electric or natural gas (defaults adjust to sensible values).
- Enter your utility rate from a recent bill.
- Enter daily hot water use and incoming/target temperatures.
- Set an efficiency assumption appropriate to your equipment.
Limitations
This estimates the energy to heat the water you use. It excludes standby tank losses, recirculation, and fixed meter charges, so your real bill is usually higher — particularly for storage tanks. Efficiency varies by model and age; use your unit’s specifications where possible.