How to Calculate the Electricity Cost of Any Appliance
Every electricity cost question comes down to one short formula. Once you know it, you can check any appliance in your home in under a minute, with nothing more than the label on the back and your last utility bill.
The formula
Watts ÷ 1,000 × hours used × price per kWh = cost.
Dividing watts by 1,000 converts them to kilowatts. Multiplying by hours gives kilowatt-hours (kWh), which is the unit your utility bills you for. Multiplying by your price per kWh turns that into dollars.
Step 1: Find the wattage
Look for the nameplate, a small label or stamped panel on the back or underside of the appliance. It will show a figure followed by W. If it shows only amps (A), multiply by the voltage: 120 for ordinary plug-in appliances, 240 for electric dryers, ranges and most water heaters.
Keep in mind that the nameplate shows maximum draw. Appliances with a thermostat or compressor, such as refrigerators, air conditioners and heaters, cycle on and off, so their average draw over time is lower.
Step 2: Estimate the hours
Be honest about run time. For always-plugged-in appliances that cycle, estimate the hours the working part is actually on. A refrigerator compressor runs perhaps 8 hours a day, not 24. For the most accurate answer, a plug-in watt meter will record real kWh over a few days.
Step 3: Find your price per kWh
Divide the total amount of your electric bill by the kWh used that month. This gives your all-in price, including delivery charges, taxes and fees, which is the number that reflects what an extra kWh really costs you. If you do not have a bill handy, use your state's average from our rates by state table.
A worked example
A 1,500-watt space heater used 6 hours a day in Ohio, where the average price is 19.45 cents per kWh:
1,500 ÷ 1,000 = 1.5 kW. 1.5 × 6 hours = 9 kWh per day. 9 × $0.1945 = $1.75 per day, or about $52.52 over a 30-day month.
You can skip the arithmetic by entering the same numbers in the calculator on our home page.
Common mistakes
Using the power supply rating for a computer instead of its actual draw. Multiplying a refrigerator's wattage by 24 hours. Using only the "supply" rate from a bill and leaving out delivery charges. Forgetting that a time-of-use plan charges different prices at different hours.