How Much Does It Cost to Run an Air Conditioner Per Hour?

The short calculation

Divide the air conditioner's input watts by 1,000, then multiply by the electricity price in dollars per kilowatt-hour. A 1,000-watt window unit at $0.18 per kWh costs about $0.18 for an hour in which it draws that full input.

Central systems often draw several kilowatts, but neither type necessarily keeps the compressor on continuously. Treat the result as a full-load estimate unless you have measured runtime or energy use.

Use input power, not cooling capacity

Cooling capacity may be shown in BTU per hour or tons, while the bill is based on electrical energy. Look for watts or amps and volts on the unit's label, manual, or specification sheet; do not enter the BTU rating as watts.

• For a plug-in unit, a wall energy meter can capture cycling over a normal day.
• For central air, use manufacturer input data or a qualified whole-home monitor.
• Include the indoor blower if its consumption is listed separately.

Convert hourly cost into a monthly range

Multiply hourly cost by estimated compressor hours per day and then by the number of cooling days. Because weather changes, a low and high runtime range is more useful than a single promise about the next bill.

What changes the real bill

Thermostat settings, humidity, insulation, duct leakage, shade, and equipment efficiency all change compressor runtime. The state average rate is a useful starting point, but your utility plan, fixed charges, tiers, and time-of-use periods can make the billed cost different.

• Compare the calculator with the energy section of a recent bill.
• Update runtime after a representative hot day instead of using a nameplate guess forever.
• Calculate fans and dehumidifiers separately when they are part of the cooling strategy.