Work out water heater running cost instantly with clear inputs, formula shown and shareable results.
Every gallon of hot water needs 8.33 BTU per degree Fahrenheit of rise. Daily volume times rise gives the useful heat, dividing by 3412 converts to kilowatt hours and dividing by efficiency accounts for what the appliance wastes. Multiplying by the tariff gives the running cost.
Energy per day
kWh = gallons x 8.33 x ΔT / (3412 x efficiency)
Annual cost
Cost = daily kWh x price x 365
kWh = gallons x 8.33 x ΔT / (3412 x efficiency). Every gallon of hot water needs 8.33 BTU per degree Fahrenheit of rise.
No. It covers only the water actually drawn. A poorly insulated tank can add another 10-15 percent for heat that leaks away between draws.
This calculator takes 4 inputs: Hot water used per day, Temperature rise, Energy price, Heater efficiency. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.