Enter the power and the use
The watts on the label, the hours per day and the number of days.
Electricity cost calculator
Enter the power of an appliance in watts, how long you use it and the price of electricity. You get the energy used and the cost per hour, day, month and year.
- Free
- No sign-up
- Runs in your browser
100% private — the calculation is done in your browser and nothing is sent to any server.
How it works
Add your electricity price
The price per kilowatt-hour from your bill.
Read the cost
Per hour, day, month and year, with the energy used.
Which appliances are costing you money?
A bill for electricity arrives as a single number, and it is hard to tell which of the things plugged in at home account for it. The cost of running any appliance can be worked out from just three numbers: how much power it uses, how long it is on and the price you pay per unit of energy. This calculator does the sum so that you can compare a heater with a fan, an old fridge with a new one, or see whether leaving a device on all day matters.
The formula
Electricity is billed in kilowatt-hours (kWh). One kWh is the energy used by a 1,000-watt appliance running for one hour. To find the energy, multiply the power in watts by the hours of use and divide by 1,000; multiply the result by the price per kWh to get the cost. A 1,500 W heater running 2 hours a day uses 3 kWh a day, which at 0.15 per kWh costs 0.45 a day, or 13.50 in a 30-day month.
Where to find the wattage and the price
The power of an appliance is normally on a label on the back or bottom, or in the manual, in watts (W) or kilowatts (kW). If it shows volts and amps, multiply them to get watts. The price per kWh is on your electricity bill; include the energy charge but bear in mind that fixed charges and taxes vary from bill to bill. The quick buttons fill in typical powers of common appliances as a starting point.
Devices that do not run constantly
Many appliances such as refrigerators, ovens, washing machines and heaters with a thermostat cycle on and off, so they do not draw their full power all the time. For these, enter the average hours of real operation, not the hours the appliance is plugged in. A fridge, for instance, typically runs its compressor for only a part of the day.
What it does not do
The tool assumes a single rate, the same at every hour. Time-of-use tariffs, fixed monthly charges, taxes, the standby power of devices that are off but plugged in and variations in power are not included. Use it for comparisons and orders of magnitude, and use your own bill for exact figures.
Frequently asked questions
How do I calculate the electricity cost of an appliance?
Multiply its power in kilowatts by the hours it runs and by the price per kWh. A 1.5 kW heater for 2 hours at 0.15 per kWh costs 0.45.
What is a kWh?
A kilowatt-hour is the energy used by 1,000 watts running for an hour. It is the unit in which electricity is billed.
Where do I find the power of my appliance?
On its label or in its manual, in watts or kilowatts. If only volts and amps are given, multiply them.
Which appliances cost the most to run?
Those that produce heat, such as heaters, kettles, irons, ovens and dryers, use far more power than lights or electronics.
Does it count the standby power?
No. Enter a small wattage and the hours it is plugged in if you want to estimate the standby consumption of a device.
Is my data sent anywhere?
No. The calculation is done in your browser.
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