A 1,500 W space heater, 8 hours a day.
1,500 × 8 ÷ 1,000 = 12 kWh a day, or 4,380 kWh a year and 365 kWh a month. At $0.17 per kWh that's $62.05 a month, $2.04 a day, or $744.60 if you ran it like that all year.
Electricity Cost Calculator
Find out what any appliance costs to run per hour, day, month and year.
Results
Enter your numbers to see the results.
- kWh per day
- kWh per month
- kWh per year
- Cost per hour
- Cost per day
- Cost per month
- Cost per year
Enter a device's wattage, how many hours a day you use it and what you pay per kilowatt-hour to see its energy use and cost per hour, day, month and year. Presets for common appliances get you started. Each uses a typical figure, so check your own device's label for its real wattage.
How to use it
- Enter the power in watts or kilowatts. If the label lists only amps, enter amps and volts and the tool multiplies them (watts = amps × volts).
- Enter how many of the device you're running, such as 6 bulbs.
- Enter how many hours a day you use it.
- Enter your electricity rate in $ per kWh. The $0.17 default is only an example. Take your real rate from your utility bill.
- For appliances that cycle on and off, like fridges and air conditioners, set a duty cycle (the share of time the compressor is actually running).
Finding your numbers
- Wattage: look for a label or nameplate on the back or bottom of the device, or in the manual. Chargers and electronics often list maximum watts, and most use less in normal use.
- Your rate: divide your bill's energy charge by the kWh used, or look for the "price per kWh" line. If your utility charges different rates at different times of day, use the rate for when you run the device.
- Exact usage: a plug-in energy meter measures real kWh for devices that vary a lot, like a fridge or a gaming PC.
How it works
Watts times hours, divided by 1,000, gives kilowatt-hours (kWh), and kWh times your rate gives the cost. If you enter amps, the tool multiplies them by volts to get watts.
- kWh per day = watts × quantity × hours per day × duty cycle ÷ 1,000. Yearly = daily × 365. Monthly = yearly ÷ 12.
Each figure is rounded to the cent on its own, so 12 × the monthly cost shown can differ from the yearly cost by a cent or two.
Worked examples
Six 10 W LED bulbs, 5 hours a day, at $0.15.
9.125 kWh a month, just $1.37, or $16.43 a year for all six. (12 × $1.37 is $16.44. The cent of difference is rounding.)
A fridge averaging 150 W, around the clock, at $0.22.
109.5 kWh a month, $24.09, or $289.08 a year. Since a fridge cycles, "average" is the key word. If you only know the compressor's running wattage, enter that with a duty cycle instead.
A 1,000 W window air conditioner, 8 hours a day, running half the time.
With a 50% duty cycle that's about 121.7 kWh a month, or $20.68 at $0.17.
A device rated in amps.
10 A at 120 V is 1,200 W. Used one hour a day, that's 36.5 kWh and $6.21 a month at $0.17.
Cost per hour of use
| Power | $0.12/kWh | $0.15/kWh | $0.17/kWh | $0.22/kWh | $0.30/kWh |
|---|---|---|---|---|---|
| 100 W | 1.2¢ | 1.5¢ | 1.7¢ | 2.2¢ | 3.0¢ |
| 500 W | 6.0¢ | 7.5¢ | 8.5¢ | 11.0¢ | 15.0¢ |
| 1,000 W | 12.0¢ | 15.0¢ | 17.0¢ | 22.0¢ | 30.0¢ |
| 1,500 W | 18.0¢ | 22.5¢ | 25.5¢ | 33.0¢ | 45.0¢ |
Shortcut: a 1,000 W device running for an hour uses 1 kWh, so it costs exactly your rate per kWh.
FAQ
How much does it cost to run a space heater?
A 1,500 W heater costs 25.5¢ an hour at $0.17 per kWh, which the tool rounds to $0.26. Run 8 hours a day, that's about $62 a month.
How do I calculate electricity cost from watts?
Multiply watts by hours of use and divide by 1,000 to get kWh, then multiply by your rate. 100 W for 10 hours is 1 kWh, which costs $0.17 at $0.17 per kWh.
What is a kWh?
A kilowatt-hour is 1,000 watts used for one hour. It's the unit your utility bills you in.
How do I find my electricity rate?
It's on your utility bill, usually as a price per kWh. If you're billed several charges, divide the total energy charges by the kWh you used for an all-in rate.
How much electricity does a refrigerator use?
It varies by model and age. A fridge averaging 150 W uses about 109.5 kWh a month. Check the yellow EnergyGuide label or measure it with a plug-in meter for your own.
Can I use this to estimate EV charging costs?
For a single charging session, yes: enter the charger's wattage and hours. For a full comparison with gas, use the EV Charging Cost vs Gas Calculator.