Method
How to calculate estimated monthly electricity cost
Watts are converted to kilowatts and multiplied by operating time. The monthly figure uses the average Gregorian month.
FORMULAMonthly cost = watts ÷ 1,000 × hours per day × tariff × 30.4375
Worked example
Electricity cost calculator example
A 1,500 W heater used 6 hours daily at $0.18/kWh consumes 9 kWh a day.
Change one assumption at a time to see what drives the result. The output is an estimate, not a quote, forecast or recommendation.
FAQ
Electricity cost calculator FAQ
Why may my utility bill differ?
Real power draw, standby use, tiered tariffs, taxes and billing periods can differ from the inputs.
What tariff should I enter?
Use the marginal or all-in price per kWh relevant to the usage you are comparing.
Does wattage stay constant?
Not always. Thermostats, compressors and variable-speed devices cycle; use measured average power where available.