How to calculate an appliance's electricity usage
- Pick an appliance from the list to load typical values, or enter the power in watts shown on its label.
- Enter how many hours per day and how many days per week you use it, and the number of appliances.
- Enter the price per kWh from your electricity bill to see the cost as well.
- Check the usage and cost per hour, day, week, month and year, and use «Compare with a more efficient appliance» to see how much you would save.
How electricity usage is calculated
The energy an appliance uses is measured in kilowatt-hours (kWh). One kWh is the energy used by a 1,000-watt (1 kW) appliance running for one hour. The math is simple: power in kW multiplied by the hours of use. A 100 W appliance left on for 10 hours uses 1 kWh.
The cost comes from multiplying those kWh by your electricity company's rate. For the month, 52 weeks divided into 12 months are used, and for the year, 52 weeks, based on the days of use you enter.
Many appliances don't draw their full power all the time: a refrigerator or an air conditioner switches its motor on and off. That's why you can enter the percentage of time they actually draw power. Everything is calculated on your device and nothing is sent anywhere.
Things to keep in mind
- The values in the list are typical and approximate. Actual consumption varies a lot with the model, its age, its efficiency class and how it is used. For better accuracy, use the figure on the appliance's label.
- Your electricity bill includes fixed charges, taxes and tiered rates that this calculator can't see: it is for comparing and estimating, not for replacing your bill.
- No rate is assumed: you enter the price per kWh in your own currency.
- Appliances on standby also use a few watts; you can add them as one more appliance.
Frequently asked questions
How do I calculate how much electricity an appliance uses?
Multiply its power in kilowatts by the hours of use. For example, a 500 W (0.5 kW) appliance used for 4 hours uses 2 kWh.
What is a kWh?
It is the unit used to measure and bill electricity: the energy a 1,000-watt appliance uses in one hour.
Where can I find the price per kWh?
On your electricity bill. If it has tiered rates, try the rate for the tier you use the most.
Why does a refrigerator use less than its power rating times 24 hours?
Because the motor doesn't run all the time: it switches on and off to keep the temperature steady. Using the percentage of time it draws power gives a result closer to reality.
Is it free? Is what I type saved?
It is free and needs no sign-up. The calculations run in your browser and no data is saved or sent.