Methodology and sources

Every figure on this site is produced by one formula, applied to published electricity prices and stated assumptions about wattage and use.

The formula

watts ÷ 1,000 × hours × price per kWh = cost

Monthly figures multiply the daily result by the number of days of use shown on the page. Yearly figures multiply the monthly result by twelve.

Electricity prices

State prices are the average price of electricity to residential customers published by the U.S. Energy Information Administration in its Electric Power Monthly (Table 5.6.A). The figures currently in use are for July 2026. The EIA calculates them as total residential revenue divided by total residential sales, so they include supply, delivery and fixed charges. The site checks for new official figures automatically every week and rebuilds every table and calculator when a new month is published, which the EIA usually does about two months after the month ends.

Wattage assumptions

Default wattages represent a typical current model, not the most or least efficient. They are based on manufacturer nameplate ratings, EnergyGuide label data and Department of Energy consumer guidance. Each appliance page also shows a range of sizes, and the calculator accepts any wattage.

Run time and cycling appliances

Appliances with thermostats or compressors do not draw their rated power continuously. For these, the "hours per day" default represents the time the heating element or compressor is actually on, not the time the appliance is plugged in or switched on. This is explained beside each calculator.

Limits of the estimates

Results are estimates for planning and comparison. Your actual cost depends on your utility, your rate plan (including tiered and time-of-use pricing), your specific appliance, your climate and your habits. For the most accurate result, enter the price per kWh from your own bill and measure the appliance with a plug-in watt meter.

Sources

Prices last refreshed: October 3, 2026.