How to use the electricity cost calculator
- Pick an appliance under Start from a common appliance, or leave it on Custom and type your own numbers.
- Enter Power (watts) from the label on the device. If the label only lists volts and amps, multiply them.
- Enter Hours per day it draws power, Days used per week and the Number of identical devices.
- Enter your Electricity rate (per kWh) from your bill and choose the currency.
- Read the cost per day of use, week, month and year, with the kWh under each. The appliance wattage chart shows what other devices cost a month at your rate, and selecting a name loads it.
How the cost is calculated
A kilowatt-hour (kWh) is one kilowatt of power used for one hour, which is how your utility meters and bills you. The U.S. Energy Information Administration explains the units.
kWh per day = watts x devices x hours / 1,000
Cost = kWh x rate
Year = day x days per week x 365 / 7, Month = Year / 12
Worked example with the default numbers
A 1,500 W appliance such as a space heater runs 3 hours a day, 7 days a week, at $0.18 per kWh. That is 1,500 x 3 / 1,000 = 4.5 kWh a day. At $0.18 it costs $0.81 per day, $5.67 a week (31.5 kWh), $24.64 a month (137 kWh) and $295.65 a year (1,643 kWh). Every hour it runs costs $0.27.
Limits and edge cases
- The label shows the maximum draw. Refrigerators, ovens, heaters and water heaters cycle on and off, so enter the hours the compressor or element actually runs. The refrigerator preset uses 150 W for 9 hours, which is 1.35 kWh a day or about 493 kWh a year.
- Heating and cooling are seasonal. The monthly figure is one month of use, so multiply it by the months you run the device.
- Standby power is small for modern devices. A dozen at 0.5 to 1 W each use 53 to 105 kWh a year, about $9 to $19 at $0.18. A dozen older ones at 5 to 15 W each use 526 to 1,577 kWh, about $95 to $284.
- Use an all-in rate: your bill total divided by the kWh you used, so delivery charges count. Time-of-use plans need an average of peak and off-peak, and fixed monthly fees are not included.
- To compare running an EV with gasoline, use the fuel cost calculator for the gas side. To convert units, try the power converter, the energy converter, or size an air conditioner with the BTU calculator.
Electricity cost questions people ask
How do I calculate how much electricity an appliance uses?
Multiply its watts by the hours you use it, then divide by 1,000 to get kWh. Multiply the kWh by your rate per kWh for the cost. A 100 W TV on for 4 hours uses 0.4 kWh, which costs about 7 cents at $0.18.
What is the average cost of electricity per kWh in the US?
The U.S. Energy Information Administration reported an average residential price of 18.31 cents per kWh for July 2026, and it forecasts about 18 cents for the year. Prices vary widely by state, so use the rate on your own bill.
How much does it cost to run a refrigerator for a year?
Most modern refrigerators use roughly 350 to 600 kWh a year, which is about $63 to $108 at $0.18 per kWh. The yellow EnergyGuide label on your model lists its own yearly figure.
My appliance is rated in BTU, not watts. How do I convert?
For an air conditioner, divide its BTU per hour by its EER to get watts. A 10,000 BTU unit with an EER of 11 draws about 910 W. For an electric heater, 3,412 BTU per hour equals 1,000 W.
Sources: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A (average retail price of electricity, July 2026 preliminary), and Measuring electricity.
Results are estimates for planning only. Actual costs depend on how you use the device, your rate plan and local charges.