How does the kWh Cost Calculator work?
The calculator multiplies the kilowatthours you enter by your electricity rate. If you only know device wattage and run time, start with the Watt to kWh Calculator or the Electricity Cost Calculator.
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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 should you enter for kWh and rate?
Use the kWh shown on a utility bill, submeter, smart plug or equipment estimate. Enter the applicable dollar-per-kWh rate and the number of days represented by that usage. For a more complete bill estimate that includes fixed charges, use the Electricity Bill Calculator.
What do the daily averages mean?
The average daily kWh and daily cost divide the period totals by the number of days you entered. They are useful for comparing periods of different lengths or checking whether changes in appliance use are moving costs. The Appliance Energy Cost Calculator can estimate the contribution of an individual appliance.
Why can a utility bill differ from kWh × rate?
Many utility bills include customer charges, taxes, riders, seasonal schedules, time-of-use rates or other adjustments. If you want to combine household electricity with natural-gas costs, use the Home Energy Cost Calculator.
Worked example: kWh Cost
Enter the following values in the kWh Cost Calculator and calculate to reproduce this result.
- Energy use: 900
- Electricity rate: 0.18
- Billing period: 30
Example result: $162.00. 900 kWh at $0.18 per kWh produces an estimated energy charge of $162.00.
Calculation used: cost = kWh × $/kWh
How to interpret this example
This calculation starts with energy already measured in kWh. Do not multiply it by operating hours again. The result is the energy charge at the entered unit rate, not a full bill including fixed charges, taxes or tariff tiers.
Frequently asked questions about kWh Cost
Multiply electricity use in kWh by the price per kWh.
Yes. A zero rate produces a zero energy charge and can be useful for testing or fully credited energy scenarios.
No. kW measures power, while kWh measures energy used over time.
Billing days are used to show average daily energy use and average daily cost.
No. It calculates the energy charge from kWh and the entered rate.
Yes. If your bill has multiple rate components, an effective average $/kWh can be useful for a simplified estimate.
The tool focuses on the entered billing period; you can compare repeated periods or use a whole-home calculator for broader planning.
It uses U.S. dollar formatting and $/kWh terminology, but the basic multiplication works anywhere when the entered rate uses the same currency basis.
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.