Core electricity formula
Energy in kWh = power in watts ÷ 1,000 × hours of use. Electricity cost = kWh × electricity rate.
Equipment that cycles
Air conditioners, refrigerators, heaters, pumps, and thermostatic equipment may not draw nameplate power continuously.
Electricity rates
State pages use residential average prices published by the U.S. Energy Information Administration for the displayed month.
Rounding
Intermediate calculations retain more precision than displayed results.
Important limitations
Results are estimates, not bills or quotes. Climate, behavior, equipment condition, and tariffs affect real cost.