Methodology & data sources
This page documents exactly where the numbers on KilowattCalc come from and how every running cost is calculated. Nothing is invented: electricity prices and appliance wattages are real published figures, and any cost we show is a transparent calculation over them.
The cost formula
We use the formula the U.S. Department of Energy publishes for appliance energy use:
daily kWh = (watts ÷ 1000) × hours per day
cost = daily kWh × days × (price in ¢ per kWh ÷ 100)
For appliances that cycle on and off rather than running at a fixed wattage (refrigerator, freezer, air conditioner, heat pump, EV charging, hot tub), we instead use a published annual-kWh figure and divide for monthly/yearly costs, so the estimate reflects realistic running rather than peak nameplate draw.
Data sources
- State electricity prices — the average residential price of electricity (cents per kWh) for all 51 US states and DC, from the U.S. Energy Information Administration (EIA) Electric Power Monthly, Table 5.6.A. Data period: March 2026. US public domain. The US average we use is 18.56¢/kWh.
- Appliance wattages — typical running wattage (or annual kWh) for 36 common household appliances, from the U.S. Department of Energy ("Estimating Appliance and Home Electronic Energy Use") and ENERGY STAR-grade public references. We show typical figures and ranges (low–high) where appropriate, and label them "typical" — we do not present a fake precise figure for a whole category.
| Source | Cadence | License |
|---|---|---|
| EIA Electric Power Monthly, Table 5.6.A — average residential price by state | none | U.S. public domain |
| U.S. DOE — Estimating Appliance and Home Electronic Energy Use | none | U.S. public domain |
| ENERGY STAR product specifications | none | U.S. public domain |
Derived figures
State rankings (most/least expensive), appliance rankings (by monthly cost and by annual kWh), the "vs US average" percentages, and every monthly/yearly running cost are computed from the inputs above — nothing else. The "typical usage" hours and days for each appliance are stated on its page and are reasonable defaults, not a claim about your household.
Limitations
These are estimates for general information. Statewide average prices hide big differences between utilities, plans and time-of-use rates; your bill's effective rate (total ÷ kWh) is the accurate one. Appliance wattages vary by model and condition, and many devices cycle. Use your appliance's nameplate wattage and your own rate in the calculator for the closest result. Always verify against the EIA, the DOE and your own bill before relying on a figure. Data as of June 2026. See our disclaimer.
Last updated: 2026-06-20