How to calculate electricity cost
kWh = Watts × Hours ÷ 1,000 Cost = kWh × Rate
A 1,500-watt space heater running 4 hours a day uses 6 kWh a day. At 17¢ per kWh, that's $1.02 a day, or $30.60 over 30 days.
Typical appliance wattage
| Appliance | Typical power |
|---|---|
| LED bulb | 8–12 W |
| Laptop | 30–70 W |
| TV | 50–150 W |
| Desktop computer | 100–300 W |
| Refrigerator | 100–250 W (cycles on and off) |
| Window air conditioner | 500–1,500 W |
| Space heater | 750–1,500 W |
| Clothes dryer | 2,000–5,000 W |
These are typical ranges. The label on your appliance gives its actual rating.
Finding your rate
Divide the total on your bill by the kWh used to get your all-in rate, including delivery charges. Rates vary widely by state and can change by season or time of day.
Frequently asked questions
What if the label shows amps instead of watts?
Multiply amps by volts. In the U.S., most outlets are 120 volts, so a 10-amp device uses about 1,200 watts.
What is a kilowatt-hour?
It's 1,000 watts used for one hour, the unit electric companies bill by.