Decision tools built for clarity
Appliance Electricity Cost Calculator
Estimate how much electricity an appliance uses and what it costs per day, month, and year at your tariff.
Enter the appliance wattage, the hours it runs per day, the days per month, and your electricity price per kilowatt-hour, then calculate.
Nameplate wattage is a maximum and many appliances cycle on and off; tiered tariffs, fixed fees, and taxes change the actual bill.
Methodology
Formula or transformation
Energy in kilowatt-hours is watts times hours per day divided by one thousand; monthly energy multiplies by the days of use; each cost multiplies energy by the tariff, and the year is twelve of the declared months.
Variables
- Power in watts
- Hours of use per day
- Days of use per month
- Tariff per kilowatt-hour
- Energy per day in kilowatt-hours
Units
- Watt
- Hour
- Kilowatt-hour
- Currency
Rounding policy
Energy and money keep canonical precision and are rounded to two decimal places for display.
Watts times hours per day divided by one thousand gives kilowatt-hours per day; the days of use give the monthly energy; each energy figure times the tariff gives the cost, and the year is twelve months.
Estimate how much electricity an appliance uses and what it costs per day, month, and year at your tariff.
Reviewed sources
- U.S. Energy Information Administration — Electricity explained: measuring electricity Reviewed on 2026-09-21
- NIST — Guide to the SI, Appendix B.8: factors for units listed alphabetically Reviewed on 2026-09-21
Formula review history
-
Initial kilowatt-hour definition and source review.
Reviewed 2026-09-21 for formula version watt-hours-to-kilowatt-hours-v1
Assumptions
- Inputs are interpreted using the displayed units and options.
- The calculation follows the methodology and factors listed in the sources.
Limitations
- Display rounding can hide additional decimal places.
- The calculation cannot add accuracy that is absent from the submitted inputs.
- Nameplate wattage is a maximum and many appliances cycle on and off; tiered tariffs, fixed fees, and taxes change the actual bill.
Worked example
A 100 W device used 5 hours a day uses 0.5 kWh per day and 15 kWh in a 30-day month; at 0.20 per kWh that is 3.00 per month and 36.00 per year.
Frequently asked questions
Where do I find the wattage?
On the nameplate or label on the back or bottom of the appliance, or in its manual; if only amperes are given, multiply them by the mains voltage to estimate watts.
Why is my bill different from the estimate?
Nameplate watts are a maximum, appliances that cycle run less than the hours you enter, and tariffs are often tiered with fixed fees and taxes.