What This Calculator Estimates
This calculator estimates the monthly electricity cost of running one appliance based on its wattage, how long you use it each day, how many days you use it in a month, and your electricity rate.
Formula / Method Used
- Convert appliance watts to kilowatts by dividing by 1,000.
- Multiply by hours used per day and days used per month to estimate monthly kWh.
- Multiply monthly kWh by your rate per kWh.
Worked Example
A 1,500-watt heater used for 4 hours per day over 30 days uses about 180 kWh in a month. At $0.15 per kWh, the estimated usage cost is $27.00.
Common Mistakes
- Entering volts or amps instead of watts.
- Ignoring the difference between actual usage hours and maximum possible hours.
- Using an outdated utility rate.
- Expecting this estimate to include taxes and fixed charges.
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Frequently Asked Questions
How does this energy cost calculator work?
It converts appliance watts to kilowatt-hours based on daily use, then multiplies the monthly kWh by your electricity rate.
What electricity rate should I enter?
Use the effective rate from your utility bill if possible, including the rate structure that applies to the appliance usage you are estimating.
Does this include taxes or fixed utility fees?
No. This page estimates usage cost only and does not add taxes, delivery fees, or fixed monthly charges.
Can I use this for any appliance?
Yes, as long as you know the appliance wattage and have a reasonable estimate of hours used per day and days used per month.
Why might the result differ from my utility bill?
Real bills may include tiered pricing, time-of-use rates, taxes, fees, and differences between nameplate wattage and actual draw.
Limitations / Disclaimer
This calculator estimates appliance energy usage only. It does not model standby power, demand charges, taxes, delivery fees, tiered utility pricing, or real-world appliance cycling behavior.
Last updated: May 23, 2026