How Much Does It Cost to Run a Window AC?
A typical 8,000-10,000 BTU window air conditioner draws about 1,000 watts while the compressor is running. At the 2024 US average rate of $0.16/kWh, that is $0.16 per hour, $1.28 for an 8-hour day, and $38.40 a month if you run it 8 hours every day. Real-world bills are usually 30-50% lower because the compressor cycles off once the room hits the thermostat setpoint.
Want the cost for a different size or your exact utility rate? Use the appliance cost calculator or see how a window unit compares to central AC on the efficiency rankings.
The Formula
Cost = (watts ÷ 1,000) × hours per day × days × price per kWh
Dividing watts by 1,000 converts to kilowatts (kW). Multiplying by hours gives kilowatt-hours (kWh) — the unit your utility bills you in. Multiply by your price per kWh and you have the cost. For an AC, the “hours” should be hours of actual compressor runtime, not just hours the unit is plugged in.
Worked example (1,000W window AC, 8 h/day, 30 days, $0.16/kWh): (1,000 ÷ 1,000) × 8 × 30 × 0.16 = 1 kW × 240 hours × $0.16 = $38.40 per month.
Monthly Cost by Hours of Use
For a 1,000W window AC (8,000-10,000 BTU) over a 30-day month at $0.16/kWh (the US average). Hours assume the compressor is actively running; thermostat cycling can reduce real-world hours by 30-50%.
| Hours per day | kWh per day | Cost per day | Cost per month | Cost per year |
|---|---|---|---|---|
| 4h | 4.0 | $0.64 | $19.20 | $234 |
| 8h | 8.0 | $1.28 | $38.40 | $467 |
| 12h | 12.0 | $1.92 | $57.60 | $701 |
| 24h (continuous) | 24.0 | $3.84 | $115.20 | $1402 |
Cost by Window AC Size (BTU)
Window AC wattage scales with cooling capacity. This table assumes 8 hours of compressor runtime per day at $0.16/kWh. A right-sized unit cycles on and off; an oversized one is shown at full power for comparison.
| Unit size | Watts | Cost per hour | Cost per month | Cost per year |
|---|---|---|---|---|
| 5,000 BTU (small bedroom) | 500 | $0.08 | $19.20 | $234 |
| 8,000 BTU (medium room) (baseline) | 1,000 | $0.16 | $38.40 | $467 |
| 12,000 BTU (large room) | 1,400 | $0.22 | $53.76 | $654 |
| 15,000 BTU (great room) | 1,800 | $0.29 | $69.12 | $841 |
Monthly Cost by Electricity Rate
Your electricity rate makes a big difference. This table shows the monthly cost of a 1,000W window AC across common rates, from low-cost states to high-rate states like Hawaii and the Northeast.
| Rate ($/kWh) | 4h/day | 8h/day | 12h/day | 24h/day |
|---|---|---|---|---|
| $0.10 | $12.00 | $24.00 | $36.00 | $72.00 |
| $0.13 | $15.60 | $31.20 | $46.80 | $93.60 |
| $0.16 (US avg) | $19.20 | $38.40 | $57.60 | $115.20 |
| $0.20 | $24.00 | $48.00 | $72.00 | $144.00 |
| $0.30 | $36.00 | $72.00 | $108.00 | $216.00 |
Monthly figures assume a 30-day month and the unit running at its full 1,000W. A properly sized AC cycles off about 30-50% of the time, so real bills run lower.
Why Window ACs Cost What They Do
The compressor is the energy hog
A window AC's fan only draws 50-100W. The compressor — which actually moves heat out of the room — accounts for 90% of the wattage. When the room hits the thermostat setpoint, the compressor shuts off and only the fan keeps running. That is why a one-degree-higher setpoint can cut runtime by 5-10%.
EER is more important than BTU
EER (Energy Efficiency Ratio) tells you BTUs of cooling per watt of electricity. A 10,000 BTU unit at EER 12 uses ~833W; the same cooling at EER 9 uses ~1,111W — roughly a third more electricity. Look for EER 11 or higher and the blue Energy Star label.
Sizing matters as much as efficiency
An oversized AC cools the air fast but shuts off before it can dehumidify, so the room feels clammy and you set the thermostat lower to compensate. An undersized unit never reaches setpoint and runs full-blast all day. ~20 BTU per square foot is a reasonable starting point for an insulated room.
Tips to Lower Your Cost
Set the thermostat to 78°F
Every degree warmer cuts cost by 3-5%. Going from 72°F to 78°F can save 20-30% a month with little comfort loss after the room is dehumidified.
Clean the filter monthly
A clogged filter cuts airflow, making the compressor run longer to remove the same heat. Five minutes of cleaning saves 5-15% on the bill.
Block direct sun on the window
Closing blinds or installing reflective film on the AC's own window prevents solar heat gain and cuts runtime by 15-25% on hot afternoons.
Seal the side panels
Foam strips or insulated panels around the unit stop hot, humid air from leaking in. See our energy savings guide.
Recommended picks
Window AC Upgrades Worth a Look
The cheapest cooling comes from the right size unit, a high EER, and a thermostat or smart plug. These categories all attack the runtime side of the cost equation.
Inverter Window Air Conditioner
Variable-speed compressor
Inverter models ramp the compressor up and down instead of cycling fully on and off, using 30-40% less electricity than a comparable fixed-speed unit.
Energy Star Window AC with Smart Plug
Schedule + thermostat
Energy Star units use about 10% less power than standard models. Wi-Fi or smart-plug control lets you cool only when you are home.
Insulated Window AC Side Panels
Reduce leakage
Most cooling loss in a window unit happens around the flimsy accordion side panels. Foam-insulated panels stop hot air from leaking in around the unit.
Reflective Window Film
Lower cooling load
Blocking direct sun on a south- or west-facing window can cut the AC's runtime by 20-30% on hot afternoons. Cheaper than upgrading the unit.
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Frequently Asked Questions
How much does it cost to run a window AC?
A typical 8,000-10,000 BTU window AC draws about 1,000W while the compressor runs. At the 2024 US average rate of $0.16/kWh, that is $0.16 per hour of compressor time. Running 8 hours a day for a 30-day summer month costs roughly $38.40. Most window ACs cycle on and off with the thermostat, so real-world bills are often 30-50% lower than these full-power numbers.
Does the BTU rating affect the cost?
Yes — directly. A 5,000 BTU unit draws around 500W, an 8,000 BTU around 1,000W, a 12,000 BTU around 1,400W, and a 15,000 BTU up to 1,800W. Pick the right size for the room: oversized units cycle off before pulling humidity out, undersized units run full-blast and never stop. The Energy Star sizing guide recommends ~20 BTU per square foot of room area as a starting point.
Does setting it higher really save money?
Yes, more than people realize. Every degree warmer you set the thermostat cuts cooling cost by roughly 3-5%, because the compressor cycles off sooner and runs fewer minutes per hour. Setting 78°F instead of 72°F can lower the monthly AC bill by 20-30% with most people not noticing the difference once the room is dehumidified.
What does the EER rating mean for cost?
EER (Energy Efficiency Ratio) is BTUs of cooling per watt of electricity. A higher EER means more cooling per dollar. A 10,000 BTU unit at EER 10 draws 1,000W, while the same cooling at EER 12 draws only 833W — about 17% less electricity for the same cooling. Energy Star window units typically have EER 11+. Over a hot-state summer, EER 12 vs EER 9 is roughly $40-$70 saved.
Is a window AC cheaper to run than central air?
For cooling one room, yes — by a lot. Central AC pulls 3,000-5,000W to cool the whole house. Running one 1,000W window unit in the room you actually use costs 1/3 to 1/5 as much per hour. The catch is comfort: window units only cool the room they are in. For a small home or one person spending most time in one space, a window unit is the cheapest cooling option.