Everyday Calculators
How to Estimate Appliance Electricity Use and Cost
Estimate monthly electricity use from wattage, daily hours, number of days, and your applicable energy rate.
Short answer
Multiply watts by daily usage hours and days, then divide by 1,000 to estimate kWh. Multiply that result by the applicable rate, remembering that taxes, tiers, fees, and discounts can change the actual bill.
Key takeaways
- Use measured or label wattage when available.
- Estimate realistic active hours, not the time the device is merely plugged in.
- Use the unit rate from your own plan or bill.
- Treat the result as an estimate rather than a guaranteed invoice amount.
Basic calculation
Monthly kWh equals watts multiplied by hours per day and days, divided by 1,000. Estimated energy cost equals monthly kWh multiplied by the entered unit rate.
| Input | Example | Meaning |
|---|---|---|
| Power | 500 W | Energy used while active |
| Daily use | 3 hours | Average active time |
| Days | 30 | Monthly usage period |
| Rate | Your bill rate | Cost per kWh |
Why the bill can differ
Real bills may include progressive tiers, time-of-use pricing, taxes, fuel adjustments, discounts, and other fixed charges.
Improve the estimate
Use a plug-in power meter for devices with variable consumption and compare several scenarios instead of relying on a single idealized number.
Official references
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Electricity Cost
Calculate monthly kWh and estimated cost