How to use
Enter the appliance’s power in watts, how many hours a day it runs and your price per kilowatt-hour. You’ll see how much energy it uses and what it costs per day, month and year. For appliances that don’t run every day (a washing machine, a sauna) set the days per week. A month is one twelfth of a year (about 30.4 days), so twelve months add up exactly to the yearly figure.
The wattage is on the appliance’s label or in its manual. If it’s given in kilowatts, multiply by 1,000: 1.5 kW = 1,500 W.
Formula
kWh = watts × hours / 1000
cost = kWh × price per kWh
Example: a 2,000 W space heater running 3 hours a day uses 6 kWh. At 17¢ per kWh that’s $1.02 a day, $31.03 a month.
Typical wattage
| Appliance | Power |
|---|---|
| LED bulb | 7–12 W |
| Laptop | 40–90 W |
| TV | 60–150 W |
| Refrigerator (24-hour average) | 30–60 W |
| Window AC | 500–1,500 W |
| Central AC | 2,000–4,000 W |
| Clothes dryer | 2,000–5,000 W |
| Space heater | 750–1,500 W |
FAQ
How do I enter power for a fridge? If you use a 24-hour average power, enter 24 hours per day: the off periods are already included in that average. If you use the power while the compressor is running, enter only its actual running time. Do not apply both adjustments.
Where do I find my rate? On your electric bill: divide the total by the kWh used to get the all-in rate, including delivery charges. The U.S. average is around 17¢ per kWh, but it varies widely by state.