Electricity CalculatorFree online other calculator — instant results, no sign-up
Energy use and cost of an appliance.
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About the Electricity Calculator
The Electricity Calculator estimates the electrical energy consumption and running cost of an individual appliance based on its power rating and daily usage. It helps homeowners and renters understand how specific devices contribute to their utility bills on a daily, monthly, and annual basis.
- Power
- The electrical power rating of the device in watts (W), typically found on the manufacturer label or power adapter (sensible range: 1 to 10,000 W).
- Hours per day
- The average number of hours the appliance is actively running each day (sensible range: 0.1 to 24).
- Price
- The electric utility cost per kilowatt-hour ($/kWh) listed on your energy bill (sensible range: $0.05 to $0.80/kWh).
Formula and method
Daily kWh = (Power / 1000) × Hours per day Daily Cost = Daily kWh × Price Monthly Cost = Daily Cost × 30 Yearly Cost = Daily Cost × 365
- PowerAppliance power consumption in watts (W)
- Hours per dayDaily operating duration in hours (h)
- Daily kWhKilowatt-hours of electricity consumed per day
- PriceUtility rate per kilowatt-hour ($/kWh)
- Monthly CostEstimated cost over a standard 30-day period ($)
- Yearly CostEstimated cost over a 365-day year ($)
The calculation divides the wattage by 1,000 to convert power into kilowatts, then multiplies by daily operating hours to find daily kilowatt-hours (kWh). Daily cost is calculated by multiplying daily kWh by the unit price. Monthly costs assume exactly 30 billing days, and yearly costs assume 365 days.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Power1500 W
- Hours per day3
- Price0.16 $/kWh
Results
- Daily kWh4.5
- Daily cost$0.72
- Monthly cost$21.60
- Yearly cost$262.80
How to use the Electricity Calculator
- 1Divide the appliance wattage by 1,000 to convert watts into kilowatts.
- 2Multiply the kilowatt rating by daily usage hours to obtain Daily kWh.
- 3Multiply Daily kWh by your electricity rate per kWh to determine the Daily cost.
- 4Multiply the daily cost by 30 for the Monthly cost and by 365 for the Yearly cost.
Reading your result
Daily kWh indicates the electrical energy load placed on your meter each day by that appliance. The cost outputs translate that consumption directly into financial terms, showing immediate daily expense alongside projected monthly and annual totals.
Limitations
The calculation assumes constant power draw at maximum wattage, which overestimates costs for devices that cycle on and off (like refrigerators, air conditioners, or heat pumps). It also assumes a flat electricity rate, ignoring tiered billing structures, seasonal adjustments, or time-of-use tariffs.
Common questions
Where can I find the wattage of my appliance?+
Wattage is usually printed on the manufacturer's nameplate, UL rating label, or power adapter. If only voltage (V) and amperage (A) are listed, multiply volts by amps to calculate approximate watts.
Why does the calculation overestimate costs for refrigerators or space heaters with thermostats?+
Thermostat-controlled appliances do not run at full power continuously; their compressors or heating elements cycle on and off throughout the day. Using the total elapsed time in a day rather than the active compressor running time yields an inflated estimate.
How does the monthly cost handle months with 28 or 31 days?+
The monthly calculation uses a fixed 30-day baseline. Months with 31 days will run slightly higher, while February will run slightly lower.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.