Electric water-heater cost calculator
Estimate the cost of an electric storage water heater, immersion heater, instant heater, or geyser using power, heating time, and tariff.
Worked calculation
A complete water heater example
3.000 kW is multiplied by scheduled time and the 100% active-runtime assumption. The inputs are examples, not claims about every device. Replace each one with the label, meter reading, schedule, and tariff that apply to you.
Water-heating cost = element kW × active heating hours × tariff3000 W · 1.5 hours/day · 7 days/week · 100% active
- Monthly energy
- 136.5 kWh
- Monthly cost
- US$24.57
- Annual cost
- US$294.84
Transparent method
The calculation
Water-heating cost = element kW × active heating hours × tariffThis planning model treats heating-element runtime as the key variable. Storage losses, inlet-water temperature, tank size, and thermostat settings determine how long the element actually runs.
Read the full methodology →Sensitivity check
Run three scenarios.
One-person useModel a shorter daily heating window.
Typical householdStart with your timer or observed element runtime.
High demandIncrease heating cycles for a larger household.
Use the result well
What can change the answer?
- Do not treat time powered on as time the element is active.
- Storage tanks lose heat between uses.
- Instant heaters draw high power for shorter periods.
Calculation standards
Visible inputs. Reproducible results.
WhoPowerCost Lab's research desk maintains the formulas, market notes, and worked examples.
HowEnergy, tariff, and behavioural assumptions stay separate so readers can replace one input without hiding the others.
WhyThe page exists to answer an operating-cost decision. Advertising never changes a formula, default, or recommendation.