Enter the wattage of an appliance, how long it runs each day and for how many days. The calculator shows the energy used in kilowatt-hours. Add your electricity price per kWh to see the cost per day, for the period and for a full year at the same use.
This calculator needs JavaScript. The formula and a worked example are below.
How to use the electricity cost calculator
Find the wattage on the appliance label or in its manual. Estimate the hours it actually runs, not the hours it is plugged in. Your price per kWh is on your electricity bill, so enter your own rate rather than relying on a national average.
The formula
Energy per day (kWh) = watts × number of appliances ÷ 1,000 × hours per day. Energy for the period = energy per day × days. Cost = energy × price per kWh.
Worked example
A 1,500 W heater runs 8 hours a day for 30 days. That is 1.5 kW × 8 h = 12 kWh a day, or 360 kWh over the month. At an example price of 0.15 per kWh, the cost is 1.80 a day and 54.00 for the month. Your own price will differ.
Why the real figure can be lower
Many appliances do not draw full power all the time. A heater or air conditioner cycles on and off with a thermostat, and a fridge only runs its compressor part of the day. For a more accurate number, use a plug-in energy meter and enter the average watts it shows.
Fixed charges, tiered rates and time-of-use pricing on your bill are not included here.
Frequently asked questions
What is a kWh?
A kilowatt-hour is the energy used by a 1,000 watt appliance running for one hour.
How do I find my price per kWh?
Look at your electricity bill. Some bills show a single rate and some show several.
Does this work for air conditioners?
Yes, if you enter the power it draws. Remember that an air conditioner cycles on and off.
Related guides
For ideas on which household items use the most, read energy-efficient appliances.