Electricity Cost Calculator
Free electricity cost calculator: how many kWh an appliance uses and its cost per day, month and year, from its wattage, hours of use and price per kWh.
Energy used
No currency is shown on purpose: the figures come out in whatever unit you type in.
What it does
An appliance's energy use is its power in kilowatts times the hours it runs: a 1,500 W heater on for 4 hours uses 6 kWh. Multiply by the price per kWh on your electricity bill to get the cost. The power is printed on the label or in the manual; for appliances with a thermostat, such as fridges and air conditioners, the motor does not run all the time, so the real use is lower than the label suggests.
How to use it
- Type the appliance's power in watts and how many hours a day it is on.
- Type the price per kWh from your electricity bill, with taxes if you want the full cost.
- Read the energy used and the cost per hour, day, month and year.
The arithmetic runs in your browser. Nothing you type is sent anywhere and nothing is stored, so you can use these with real numbers.
Frequently asked 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 only volts and amps, multiply them: 120 V × 10 A = 1,200 W. A plug-in power meter gives the real figure.
What is a kWh?
A kilowatt-hour is the energy used by something of 1,000 watts running for one hour, and it is the unit your electricity bill charges for. A 100 W bulb takes 10 hours to use 1 kWh.
Do appliances use power when switched off?
Many do, in standby: TVs, chargers and set-top boxes often draw 0.5 to 5 W all day. Type that power and 24 hours to see what standby costs in a year.
Why is my bill different from the calculation?
Bills add fixed charges, taxes and sometimes tariffs that change by time of day or by how much you use. For an exact figure, divide the total of the bill by the kWh used and use that as the price.