How does the Electricity Cost Calculator work?
This calculator converts electrical power in watts to kilowatts, multiplies by operating time to estimate kilowatthours (kWh), and then multiplies kWh by the electricity rate you enter. If you already know the energy use in kWh, the kWh Cost Calculator is the faster option.
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For optional supporting equipment or reference material, you can browse Plug-in electricity meters (paid link) on Amazon.com. Use only with compatible plug-in appliances within the meter rating. It is not a whole-building meter and must not be used to modify wiring or test exposed mains. No purchase is required to use this calculator.
What values should you enter?
Use the rated or measured wattage for the device, the average hours it runs each day, the number of days in the period, and the price you pay per kWh. For equipment that cycles on and off, the Appliance Energy Cost Calculator adds a duty-cycle input, while the Air Conditioner Energy Cost Calculator is tailored to cooling loads.
How should you read the result?
The main result is the estimated electricity cost for the period you entered. The detail cards show daily energy use, total kWh and daily cost so you can compare scenarios. To model a complete monthly utility bill with fixed charges and percentage-based fees, use the Electricity Bill Calculator.
What can make the real cost different?
Real devices may draw more or less power than the nameplate value, operating time can vary, and utility rates can include tiers, time-of-use prices, demand charges, taxes or credits. For whole-home planning that combines electricity and natural gas, use the Home Energy Cost Calculator.
Worked example: Electricity Cost
Enter the following values in the Electricity Cost Calculator and calculate to reproduce this result.
- Power draw: 1500
- Hours used per day: 5
- Number of days: 30
- Electricity rate: 0.18
Example result: $40.50. 225 kWh over 30 days at $0.18 per kWh costs about $40.50.
Calculation used: cost = (watts ÷ 1,000) × hours/day × days × $/kWh
How to interpret this example
Watts describe power; kWh describe energy over time. Divide watts by 1,000 before multiplying by operating hours. This estimate covers the modeled energy charge only, so it need not equal a bill that also includes fixed fees or taxes.
Frequently asked questions about Electricity Cost
Cost = (watts ÷ 1,000) × hours per day × days × electricity rate per kWh.
A kilowatthour is the amount of energy used by one kilowatt of power for one hour.
Enter watts. The calculator converts watts to kilowatts automatically by dividing by 1,000.
Check your utility bill for the energy rate or an effective per-kWh rate. Some bills use multiple rates, so choose the rate that best matches the scenario.
No. This tool estimates the energy charge from kWh use. Use the Electricity Bill Calculator when you want to include fixed charges and percentage-based fees.
Yes, but cycling equipment may not run at full rated power continuously. A duty-cycle calculator can give a more realistic scenario.
A utility bill may include other appliances, fixed customer charges, taxes, riders, tiered pricing or time-of-use rates.
The calculation runs in your browser and the page does not require an account for the calculation.
Sources and methodology
The calculator uses the transparent formula described on this page and the values you enter. These authoritative U.S. resources provide context for electricity, home energy, solar, efficiency or safety topics related to this tool.