How We Calculate Running Costs
Every running cost on this site comes from the same simple sum, with the inputs shown so you can redo it with your own electricity rate.
The formula
Cost = power (kW) × hours of use × price per kWh
Power in watts is divided by 1,000 to get kilowatts. A 1,500 W hairdryer used for 10 minutes a day uses 1.5 kW × (10 ÷ 60) h = 0.25 kWh a day, or about 91 kWh a year.
Where the numbers come from
- Annual energy use (kWh/year) for fridges, freezers, air conditioners, dehumidifiers and air purifiers comes from the ENERGY STAR certified product data, published by the US Environmental Protection Agency and based on standard lab tests.
- Electricity price: we use the US average residential price of 18.31¢ per kWh (July 2026), from the US Energy Information Administration (source). Your own rate may be higher or lower; check your bill.
- Wattage of small appliances (kettles, toasters, air fryers) that ENERGY STAR does not certify comes from manufacturer specifications and our own plug-in meter measurements. Where we measured it ourselves, the article says so.
Assumptions
- Usage hours are stated on each page. Change them to match how you use the appliance.
- ENERGY STAR figures come from standard tests. Real use (room temperature, door openings, load size) changes them.
- ENERGY STAR lists only certified models sold in the US and Canada, so uncertified models are not included in our model tables.
Corrections
If you think a figure is wrong, tell us. We update the page and its "Updated" date.