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Electricity Cost Calculator
Work out what an appliance costs to run per day, month, and year from its wattage, the hours you use it, and your price per kWh, in your own currency.
Electricity Cost Calculator: Energy is power multiplied by time: watts times hours a day, divided by 1,000, gives kilowatt-hours a day, the method the US Department of Energy describes. Multiplying by your price per kWh gives the cost. If the label gives amps and volts instead of watts, multiplying them gives the watts. Runs 100% locally in your browser with zero server file uploads.
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The label only shows amps and volts
Your electricity bill shows the price per kWh, sometimes called a unit.
From watts to a bill
A watt is a rate of using energy; a kilowatt-hour is 1,000 watts for one hour, the unit on the bill. A 2,000 W heater running for 3 hours uses 6 kWh; at 0.30 a kWh that is 1.80. The same arithmetic covers everything from a phone charger to a car: watts times hours, divided by 1,000, times the price.
The label states the most power an appliance draws. Heaters and kettles draw it the whole time they are on, but fridges, freezers, and air conditioners switch on and off to hold a temperature, and computers and televisions draw less when idle, so for those the result is an upper limit. A plug-in energy monitor shows what they really use.
Reading your price
Bills usually show two charges: a price per kWh, which grows with use, and a standing or daily charge, which does not. Only the first belongs in this calculation. Where the price changes with the time of day, use the rate for the hours the appliance runs, for example the night rate for a car charging overnight.
To compare running costs between two appliances, work out each one's yearly cost; for the price of a product per unit or per kilogram, use the unit price calculator.
How to use it
- Pick an appliance as a starting point, or enter the wattage from its label.
- Enter how many hours a day and days a week you use it.
- Enter your price per kWh from your bill, and read the cost per day, month, and year.
Privacy & limitations
Everything is calculated in your browser. Your price and currency are kept in this browser for next time.
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Frequently asked questions
Where do I find the wattage?
On the label or nameplate, usually on the back or underneath. If it only shows amps and volts, multiply them: 10 A at 230 V is 2,300 W. The label gives the most power the appliance draws, so the estimate is an upper bound for appliances that cycle on and off.
Why does a fridge use less than its wattage suggests?
A fridge's compressor switches on and off to hold the temperature. The DOE guide suggests counting a third of the time it is plugged in, about 8 hours a day. For a new fridge, the yearly kWh on its energy label is the better figure.
Where do I find my price per kWh?
On your electricity bill, as the price per kilowatt-hour or per unit. Leave out the standing or daily charge, which you pay however much you use.
How accurate is it?
As accurate as the wattage and hours you enter. For the exact figure, a plug-in energy monitor measures what an appliance really uses over a week.
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