Calculator tool
How this calculator works
Use the explanation to understand the formula, assumptions, and practical limits behind the calculator result.
From Watts to Electricity Cost
Electric bills charge for energy used, not only the power rating printed on an appliance. The calculator first turns watts into kilowatt-hours:
Then it multiplies that energy by the electricity price.
A Simple Example
A 100-watt device used for 5 hours per day uses:
If electricity costs 0.15 per kWh, that device costs 0.075 per day before taxes or other bill charges.
Why Monthly Cost Is Only an Estimate
The tool uses 30 days for monthly cost and 365 days for yearly cost. Real bills may use different billing periods, tiered prices, taxes, or fixed charges.
Appliance Behavior Matters
Some devices run steadily, while others cycle on and off. For a better estimate, use average measured wattage when you have it instead of relying only on the label value.
Frequently asked questions
Why divide by 1,000?
Because utility bills use kilowatt-hours, and 1 kilowatt = 1,000 watts. The conversion changes appliance power into the energy unit used for billing.
Should I use rated watts or measured watts?
Measured average watts are better when available, especially for devices that cycle on and off. The nameplate rating can be higher than typical use.
Why might my bill still be higher than the calculator result?
Your bill may include other appliances, fixed charges, taxes, tiered tariffs, seasonal pricing, or a billing period that is not exactly 30 days.
Can I compare two appliances with this calculator?
Yes. Use the same hours and price assumptions for both, then compare daily or yearly cost instead of wattage alone.
