How the calculation works
Energy (kWh) = electrical input (kW) × operating hours. Multiply energy by your electricity price to estimate cost. Divide watts by 1,000 to convert to kilowatts.
The starting example is 3 kW × 8 hours × 30 days = 720 kWh. At an illustrative $0.18/kWh, that is $129.60 per month, or $0.54 per operating hour. Those figures describe the entered scenario, not a national average.
Use actual electrical input
A three-ton air conditioner has a cooling capacity; that does not mean it consumes 3 kW. Use measured electrical draw or suitable manufacturer operating data. If your measurement excludes the indoor blower, add its consumption separately. Do not open electrical panels or attempt live measurements yourself.
For cycling equipment, enter hours when the compressor is actually operating. For a variable-speed system, use an average draw that represents the period, or calculate several operating conditions separately. Treating eight thermostat-enabled hours as eight full-power hours can overstate consumption.
What this estimate leaves out
Fixed utility service fees generally do not change because the AC runs longer. Time-of-use pricing needs separate calculations for each rate period. Weather, thermostat settings, equipment condition, and indoor humidity can change runtime. This tool calculates a chosen scenario; it does not forecast the weather or size equipment.
Calculation model reviewed October 21, 2026. Original worked examples by the Everyday Cost Lab editorial desk. Estimates do not replace a contractor’s assessment.