Electricity cost calculator
What an appliance costs to run per day, month and year.
About this calculator
This electricity cost calculator shows what an appliance or device costs to run. Enter its power in watts, how many hours a day you use it and your electricity price per kWh.
Use it to compare heaters, air conditioners, fridges, computers or chargers, and find where your energy bill goes.
How it works
Energy in kilowatt-hours is watts × hours ÷ 1,000. The cost is the energy × your price per kWh, which you can find on your electricity bill.
Last reviewed:
Worked example
- Power: 1,500 watts
- Hours used a day: 3 hours
- Days used a month: 30 days
- Price per kWh: $0.17
Cost a month: $22.95
Common questions
How do I find an appliance's wattage?
Look at the label on the back or bottom, or in the manual. If it shows amps and volts, multiply them to get watts.
What is a kWh?
A kilowatt-hour is 1,000 watts used for one hour, such as a 1,000-watt heater running for an hour. It's the unit on your electricity bill.
What uses the most electricity at home?
Usually heating and cooling, water heating, and large appliances such as tumble dryers and ovens. Small devices on standby add up too.
Sources and further reading
The story behind it
Where the idea came from: Electricity was first sold by meter in the 1880s, when companies such as Thomas Edison's began charging customers for what they used.
Edison's early meters used plates in a chemical solution that gained weight as current passed, and they were weighed to work out the bill. The kilowatt-hour soon became the standard unit. It is still what your bill counts and what this calculator works out.
Why you can trust this calculator
- It runs in your browser. Nothing you type into it is sent anywhere.
- The method is explained on this page, so you can check it yourself.
- Free to use, with no sign-up.
- Results are estimates, so please double-check anything important.
- Spotted a mistake? Tell us and we'll look into it.
After 15 years as a mathematics educator, I built CalculStore to give students, teachers, professionals and anyone working with numbers simple, reliable tools.
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