Methodology & sources

Appliance wattages

Running and starting watts for each of the 36 appliances are checked against at least two published sources: generator manufacturers' wattage charts (Champion, Honda, Generac), EcoFlow's appliance chart and the U.S. DOE's typical-wattage list. Where ENERGY STAR publishes measured power (TVs, ceiling fans, window ACs), it counts as a source too. Our low, typical and high figures must fall inside the range the sources give, or the site doesn't build until a person reviews the difference. Every appliance page lists each source's figure.

Real-model data

For refrigerators, freezers, TVs, dehumidifiers, window ACs, dishwashers, washers, dryers and ceiling fans we use the ENERGY STAR certified products database (U.S. EPA): rated annual kWh or measured watts for every certified model, summarised by type and size. Certified models are more efficient than average, so older units typically use more.

Electricity rates

Average residential price per kWh for each state and the U.S. from the EIA Electric Power Monthly, Table 5.6.A, currently August 2026. Rates vary by utility, plan and season; use your own rate from your bill for precision.

Formulas

kWh/day = watts × hours/day × duty ÷ 1,000
cost/year = kWh/day × days/year × rate

Duty is the share of time the appliance actually draws its running watts: about one third for refrigerators and freezers (U.S. DOE guidance), 1 for everything else. Battery runtime = capacity (Wh) × 0.85 ÷ average watts. Generator/power-station peak = total running watts + the single highest starting watts (Generac's worksheet method).

The calculations are checked against the DOE's published worked examples (an electric kettle at 1,500 W for an hour a day costs $60.23 a year at 11¢/kWh) before every update.

Updates

An automated job re-downloads the EIA rates and ENERGY STAR data every month, re-runs all checks, and alerts us to large changes.

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