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Electricity Cost Calculator

Calculate the daily, monthly and annual running cost of any appliance from its wattage and usage.

Formula verified 3+ known-answer test cases Last verified August 2026

Power unit

Power

Usage hours/day

Number of days

Electricity rate ($/kWh)

Standby wattage (optional)

Result

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How to use the Electricity Cost Calculator

Enter the appliance's power draw and choose watts or kilowatts.
Enter how many hours per day it actually runs.
Enter the number of days you want costed (30 for a month, 365 for a year).
Enter your electricity rate per kWh from your utility bill.
Select Calculate to see daily, monthly and annual cost.

Formula

Energy and cost

Energy (kWh) = power (kW) × hours
Cost = kWh × tariff

Worked example

Verified example QA passed

Power: 1,000 W (1 kW)
Usage: 2 hours/day for 30 days
Rate: $0.20/kWh

Energy = 1 kW × 2 h = 2 kWh/day
Total = 2 kWh × 30 days = 60 kWh
Cost = 60 × $0.20 = $12

Result: 60 kWh, $12 for the period

Why this matters: Appliance-level cost estimates help identify which devices are actually driving a high electric bill, instead of guessing based on which one feels like it uses the most power.

Common mistakes

Entering an appliance's maximum rated wattage instead of its typical running wattage, which overstates the cost.
Forgetting to convert watts to kilowatts before multiplying by hours run.
Ignoring standby draw on devices that are rarely fully powered off, which can add up over a full year.

Frequently asked questions

How do I convert watts to kilowatt-hours?

Divide watts by 1,000 to get kilowatts, then multiply by the hours the appliance runs to get kWh.

What is a typical electricity rate per kWh?

Rates vary widely by region and provider, commonly ranging from about $0.10 to $0.30 per kWh. Check your utility bill for your exact rate.

Does standby power matter for the total cost?

It can add up. Many devices draw a small standby load even when off; over a full year that can meaningfully affect the annual total for some appliances.

Related calculators

Formula reviewed against the site calculation methodology. Read our formula reference library or report an issue via contact. For more background, see kWh Explained: What a Kilowatt-Hour Actually Measures.