Use your appliance power input, electricity rate and realistic usage pattern. No national “live price” is assumed.
Cost = power in kW × usage hours × electricity rate in USD per kWh. An optional duty cycle can model compressor cycling, but it remains an estimate.
The formula is exact arithmetic; the future runtime, cycling and rate-plan inputs are still assumptions.
Enter the appliance or matched system’s rated electrical input, not cooling capacity in BTU/h. Watts describe electric demand; BTU/h describes heat moved. For variable equipment, one nameplate or brochure value may not represent every operating point.
Compare mild, typical and extreme-use hours rather than treating one day as an annual forecast. Weather, room load, thermostat setting, insulation, air leakage, humidity and cycling can change actual consumption.
Dividing the same billing cycle’s total bill by kWh gives an implied all-in rate. Fixed fees, tiers, time-of-use periods, demand charges, credits and taxes may make a simple flat-rate scenario differ from the next bill.
The result excludes repairs, purchase cost, maintenance and financing. It is not an electricity-plan quote, savings guarantee or weather-normalized forecast.