How it works
How to calculate it
The calculator applies the values you enter to this formula:
Energy = watts ÷ 1,000 × daily hours × days; cost = energy × rate.
How to use this calculator
- Enter rated or measured wattage.
- Estimate daily active runtime.
- Apply the relevant billing-period rate.
Worked example
A 1,500 W appliance used one hour a day consumes 45 kWh over 30 days.
Important assumptions
- Rated wattage may differ from average consumption.
- Standby power is excluded.
- Cycles, thermostats, and variable-speed motors reduce actual runtime.
Common mistakes to avoid
- Assuming maximum wattage is the average.
- Leaving out standby consumption when it matters.
- Comparing appliances over different time periods.
Method reviewed June 10, 2026. Prices and rates are user-provided defaults and should be replaced with local values.