Electricity Cost Calculator
Estimate the monthly electricity cost of any appliance by entering its wattage, daily usage hours, and your utility rate. Ideal for budgeting energy bills or comparing the running costs of devices.
About this calculator
This calculator converts an appliance's power draw from watts to kilowatts, multiplies by daily usage hours to get daily energy consumption in kWh, then scales to a 30-day month and applies your electricity rate. The core formula is: Monthly Cost = (Power (W) / 1000) × Hours/day × Rate ($/kWh) × 30. For example, a 1,000 W device running 5 hours a day at $0.13/kWh costs $19.50 per month. Understanding kWh is key — one kilowatt-hour is the energy used by a 1,000 W appliance running for one hour. Utility companies bill in kWh, so converting watts first is essential. This formula gives a straightforward monthly estimate assuming consistent daily use.
How to use
Suppose you want to find the monthly cost of a 1,500 W space heater run 4 hours per day at an electricity rate of $0.12/kWh. Step 1 — Convert watts to kilowatts: 1,500 / 1,000 = 1.5 kW. Step 2 — Multiply by daily hours: 1.5 × 4 = 6 kWh per day. Step 3 — Multiply by 30 days: 6 × 30 = 180 kWh per month. Step 4 — Apply the rate: 180 × $0.12 = $21.60 per month. Enter 1500, 4, and 0.12 into the calculator to confirm this result instantly.
Frequently asked questions
How do I calculate the monthly electricity cost of an appliance at home?
To find the monthly cost, multiply the appliance's wattage by the hours used per day, divide by 1,000 to convert to kWh, then multiply by your electricity rate and by 30 days. The formula is: Cost = (W / 1000) × hrs × rate × 30. You can find your electricity rate on your utility bill, typically expressed in cents or dollars per kWh. This calculator automates all those steps so you get an instant result.
What is a typical electricity rate used when estimating energy costs?
In the United States, the average residential electricity rate is approximately $0.12–$0.16 per kWh, though it varies significantly by state and provider. States like Hawaii can exceed $0.30/kWh while some southern states are closer to $0.09/kWh. Always check your most recent utility bill for the exact rate applied to your account. Using an accurate rate gives you a much more reliable monthly cost estimate.
Why does the calculator multiply by 30 instead of the actual days in the month?
Multiplying by 30 is a standard approximation used to represent an average calendar month, since months range from 28 to 31 days. For most budgeting purposes this introduces a negligible error of at most 3–4%. If you need a more precise figure for a specific month, you can manually calculate by multiplying the daily cost by the exact number of days. The 30-day convention is widely used by utility estimators and appliance energy-label calculators worldwide.