How the Electricity Cost Calculator works
Last data update: 2026-08-24 (rates for May 2026).
Data
State rates: EIA Electric Power Monthly, Table 5.6.A, residential sector, data month May 2026 (released July 23, 2026), stored in state-tariffs.csv at EIA's two-decimal precision. The US average (18.44 ¢/kWh) was read directly from EIA's Electricity Monthly Update; state values were transcribed from two independent republications of Table 5.6.A that agree to the cent, because EIA's table page was unavailable at collection time. The file is refreshed when each new monthly table is published.
Appliance wattages: appliance-watts.csv (see the generator calculator methodology).
Household consumption reference: EIA FAQ 97 — 10,791 kWh/year, ~899 kWh/month (2022 figure as published at collection time).
Formula
kwh_day = watts / 1000 × hours × duty_cycle
cost_day = kwh_day × rate_cents / 100
cost_month = cost_day × days_per_month // default 30
cost_year = cost_day × 365
Limits
State averages are not your tariff; time-of-use plans, tiered rates, and fixed charges change the marginal cost. Duty cycle is a user estimate.
Change log
- 2026-08-24 — first release; May 2026 rates.
Cite this page
GridComfort, "Appliance Electricity Cost Calculator — methodology," https://gridcomfort.com/tools/electricity-cost-calculator/methodology/, data updated 2026-08-24.