Electricity Cost Calculator

Convert average device wattage and run time into kilowatt-hours and an estimated bill contribution.

Free to useCalculated in your browserv0.2.1 · Method documented September 12, 2026

Your inputs

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Know the limits. Rates are user-supplied. This excludes fixed charges, tiered tariffs, demand charges and time-of-use differences.

How it works

A device averaging 120 W for 5 hours a day uses 0.6 kWh daily. Over 30 days, that is 18 kWh or $2.70 at the illustrative $0.15/kWh rate.

Energy = watts ÷ 1,000 × hours/day × days
Cost = energy × price/kWh

Try the example

The starter inputs above produce:

Estimated electricity cost: $2.70

Change the inputs to match your own situation. The result is an estimate or text transformation, not a substitute for reviewing your source data.

A few useful details

Should I use the power-supply rating?

The calculator expects actual average consumption. A power supply’s maximum capacity is not the same as the device’s average draw.

Can I estimate one day?

Yes. Set days to 1 and enter the number of operating hours for that day.

Do I need an account?

No. This release runs without an account, API key or payment. Saving a favorite stores only the tool’s identifier in this browser, not your inputs.