Electricity Cost Calculator

1. Find your appliance's wattage. Check the label on the back or bottom of the device, the owner's manual, or click any row in the appliance table to auto-fill the wattage. Common examples: a refrigerator uses about 150 watts, a window AC unit uses 900 to 1,500 watts.
2. Enter hours used per day. Be realistic. A refrigerator runs roughly 8 hours out of 24 (its compressor cycles on and off). A TV might run 4 hours per day. A space heater might run 3 hours.
3. Set days per month. For appliances that run every day, use 30. For appliances used only on weekdays, use 22.
4. Enter your electricity rate. Find this on your monthly utility bill, usually listed as cents per kWh. The US average is about $0.13/kWh but ranges from $0.09 in Louisiana to over $0.30 in Hawaii and California.

Example: a 1,500-watt space heater running 4 hours per day at $0.15/kWh costs 1,500 × 4 / 1,000 × $0.15 = $0.90 per day, about $27 per month.

kWh per day   = Watts × Hours per day / 1,000
kWh per month = kWh per day × Days per month
Monthly cost  = kWh per month × Rate ($/kWh)
Annual cost   = kWh per day × 365 × Rate

Example: 55-inch LED TV

Wattage:        100 watts
Usage:          5 hours per day, 30 days/month
Rate:           $0.13/kWh

kWh/day   = 100 × 5 / 1,000    = 0.5 kWh
kWh/month = 0.5 × 30           = 15 kWh
Monthly   = 15 × $0.13         = $1.95/month
Annual    = 0.5 × 365 × $0.13  = $23.73/year

Kilowatt-hours (kWh) are the unit electric utilities use to measure energy consumption. One kWh = 1,000 watts used for 1 hour. A 100-watt bulb burning for 10 hours uses 1 kWh. Your monthly electricity bill is the sum of kWh used by every device in your home multiplied by your per-kWh rate.