Calcwise / Everyday / Electricity cost calculator
Electricity cost calculator
Enter the power of a device, how many hours a day it runs and your price per kWh.
Calculated in your browser. Nothing you enter is sent or stored.
About this tool: Electricity cost calculator
The label on an appliance shows its power in watts. Electricity is billed in kilowatt-hours (kWh): the energy used when 1,000 watts run for one hour. Multiply power by running time and by your tariff to see what a device costs.
The result assumes the device draws its rated power the whole time it runs. Many devices, such as fridges and heaters with a thermostat, cycle on and off, so real use is often lower.
Formula
Energy (kWh) = power in W ÷ 1,000 × hours per day × days. Cost = energy × price per kWh.
Worked example
A 2,000 W heater for 2 hours a day over 30 days: 2 × 2 × 30 = 120 kWh. At 1.10 per kWh that is 4.40 a day, 132.00 for the period and 1,606.00 per year.
Sources and data
- Formulas and data last reviewed
- Accuracy
- The result is plain maths: with valid input it is exact, and we only round to cents.
Frequently asked questions
How do I find the price per kWh?
It is on your electricity bill, usually including distribution fees and taxes. Use the total per kWh for the most realistic result.
Why is my real bill lower than the result?
Devices with a thermostat do not run at full power all the time, so the rated power overstates their use.
What is standby power?
Many devices use a few watts when off. Enter that small power and 24 hours to see what leaving it plugged in costs.