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Estimate electricity usage and monthly running cost from watts and usage time.
Use this electricity cost calculator to estimate how much an appliance costs to run. Enter the device power in watts, average daily usage hours, and your electricity rate per kWh to see daily usage, monthly cost, and yearly cost. The calculator is designed to give a fast answer, but the quality of the answer still depends on accurate inputs and a clear idea of what decision you are trying to support.
- Enter Power Rating, Hours Used per Day, and Electricity Rate using the same units you plan to compare or report.
- Read the main estimated monthly cost first, then use the supporting outputs to understand the trade-offs behind that result.
- Compare your numbers with the worked examples below if you want a quick reasonableness check.
The result turns power draw into an actual money estimate, which makes it easier to compare appliances than looking at watts alone. On this page, the primary output is estimated monthly cost.
Scenario 1: 1,500 W heater used 5 hours a day at $0.20 per kWh. Inputs used: powerWatts: 1500, hoursPerDay: 5, ratePerKwh: 0.2. Example result: $45.00 estimated monthly cost. This heater uses about 7.5 kWh per day, which translates to roughly $45 per month and $547.50 per year at the selected electricity price. Scenario 2: 350 W device used 24 hours a day at $0.15 per kWh. Inputs used: powerWatts: 350, hoursPerDay: 24, ratePerKwh: 0.15. Example result: $37.80 estimated monthly cost. A device drawing 350 watts continuously uses about 8.4 kWh per day, which costs about $37.80 per month at this rate.
Core formula: daily kWh = (watts / 1000) * hours; cost = kWh * rate. The calculator converts appliance wattage into daily energy use, then applies your electricity rate to estimate recurring cost over longer time periods.
- The model assumes the appliance draws the same power whenever it is on.
- Bills can differ if tariffs change by time of day or include fixed charges.
Use this calculator when budgeting household energy use, comparing appliances, or checking whether an always-on device is costing more than expected. Related paths for follow-up analysis include temperature converter, concrete calculator, savings calculator, and hourly to salary calculator.
Most bad outputs come from a few repeated input errors or interpretation mistakes. Use this short checklist before relying on the result.
- Using label wattage when real-world power draw changes during operation.
- Ignoring standby use or duty cycles for devices that switch on and off.
- Comparing estimated running cost without checking the actual tariff on the utility bill.
