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How the calculation works
Energy (kWh) = power (W) × hours/day × days ÷ 1000. Cost = kWh × local rate.
KEY FORMULAEnergy (kWh) = power (W) × hours/day × days ÷ 1000. Cost = kWh × local rate.
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Worked example
A 150 W device running 8 hours per day for 30 days uses 36 kWh; at 0.20 USD/kWh, it costs about 7.20 USD.
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Before you rely on this result
Real power may vary with duty cycle and efficiency. Use the rate from your bill; the example is not an official utility rate.
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Informational tool. It does not replace testing, measurement or professional advice when needed.
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Frequently asked questions
Does this work for refrigerators?+
Yes, but compressors cycle on and off. Measure actual energy use for more accurate costs.
Does it include taxes?+
It only multiplies kWh by your entered rate. Add other bill charges separately.