1000 W for 3 h/day
- Energy
- 90 kWh
- Days
- 30
- Rate
- $0.16 per kWh
Electricity Calculator
Use this free electricity calculator to estimate kilowatt-hours and cost for an appliance or device from wattage and usage time.
Research-backed assumptions Formula steps Examples included Private in-browser use
Formula steps
- Convert watts to kilowatts by dividing by 1,000.
- Multiply by hours per day and number of days to get kWh.
- Multiply kWh by your electricity rate.
How to use the electricity calculator
- Enter watts, hours per day, days, and your rate per kWh.
- Press Estimate electricity cost to see kWh and cost.
- Use your real utility rate when you want a closer estimate.
- Remember bills can include taxes, fees, tiered rates, and variable device power.
Common uses
Estimate appliance energy use.
Compare a heater, AC, computer, or light over time.
Turn watts and usage time into kWh.
Multiply kWh by your local rate.
Examples
$28.80
Low yearly estimate
Monthly energy cost
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the Electricity Calculator?
Use it when your task matches one of these common needs: Estimate appliance energy use. Compare a heater, AC, computer, or light over time. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Electricity Calculator doing with my inputs?
In plain language: The calculator divides watts by 1,000 to get kilowatts, multiplies by hours and days for kWh, then multiplies by the rate per kWh. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
Real bills include taxes, fees, tiered rates, demand charges, standby use, and variable device power draw. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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