How much does it cost to run a window air conditioner?

A typical 900-watt window unit cycling about 60% of the time costs roughly 9 to 12 cents per hour at the U.S. average rate — around $30 to $50 a month if run heavily through the cooling season.

Is a window AC cheaper to run than central air?

For cooling one or two rooms, yes, considerably. A window unit draws a fraction of the power of a whole-house central system, so if you only need to cool the rooms you're using, running a window AC and leaving central air off is usually the cheaper approach.

Does the size of a window AC affect running cost?

Yes — a larger, higher-BTU unit draws more power per hour, but an undersized unit runs constantly without cooling well, which can cost more in the end. Matching the unit's capacity to the room size keeps both comfort and running cost in the efficient range.

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Window AC Electricity Cost Calculator

A window air conditioner is a far smaller electricity user than central AC, but for people cooling one or two rooms it's the main summer cost. A typical unit draws around 900 watts while running and cycles on and off to hold the room temperature. This calculator applies that duty cycle and shows what your window AC costs to run per hour, day, and month at your electricity rate.

Appliance

Wattage(W)

Quantity

Usage measured in

Usage

Duty cycle (share of time actually drawing power) 60%

State (auto-fills rate)

kWh / day

4.32kWh

watts × hours × duty ÷ 1000

Cost / month

$22.03

at your state rate

Cost / year

$268

this appliance

Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.

How we calculate this →

Build a whole-home estimate item by item.

Window AC costs: smaller unit, comparable math

A 5,000 BTU window unit draws about 450–500 W; a 10,000 BTU unit about 900–1,000 W; a 14,000 BTU unit about 1,200–1,400 W. Like all compressor-driven devices, window ACs cycle on and off — a 50% duty cycle is typical in moderate weather, meaning the compressor runs about half the time while the fan runs continuously.

Running three window units (900 W each at 50% duty) for 10 hours daily costs about $14/month at the U.S. average rate — considerably less than central AC, but it adds up when you're cooling multiple rooms. Energy Efficiency Ratio (EER) varies meaningfully across models: a 12 EER unit uses 30% less electricity than a 9 EER unit of the same BTU capacity. When buying, a higher EER rating pays back quickly in warm climates.

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