Window AC Cost Per Month Calculator
Enter your window unit's BTU and CEER (or its watts) and the hours the compressor runs, and get the cost per hour, day and month in your state.
Window AC cost
A03Scenario A
Sets the electricity rate. Pick US average if you're not sure.
From EIA for US average. Use the rate on your bill if you know it.
Rate used: 18.4¢/kWh · US average · EIA reference 2025–26 (data as of 2026-09-26) ·
On the front label or the box.
Combined Energy Efficiency Ratio, on the yellow EnergyGuide label.
Hours the compressor runs, not hours the unit is on.
Estimated cost per month
- Running watts (BTU ÷ CEER)727 W
Per year assumes the same use every day.
Estimate. Formula and sources are under “How it works”. Change any input; the result updates as you type.
Formula
How it works
- Watts = BTU ÷ CEER
- kWh per day = watts ÷ 1,000 × compressor hours
- Cost per hour = watts ÷ 1,000 × rate
- Cost per month = kWh per day × days × rate
CEER is BTU of cooling per watt-hour, so dividing capacity by CEER gives the power the unit draws while the compressor is running. An 8,000 BTU unit with a CEER of 11 draws about 730 W; a 12,000 BTU unit about 1,100 W. The thermostat cycles the compressor, so 8 hours of compressor time a day is roughly 12–14 hours of the unit being switched on.
Sources: watts = BTU ÷ CEER (AHAM/DOE test definition). Federal standard since 2023: CEER of at least 11 for an 8,000 BTU unit. Electricity rate: EIA Electric Power Monthly table 5.6.A.
Worked example
A worked example
A 12,000 BTU window unit with a CEER of 12 draws 12,000 ÷ 12 = 1,000 W. With the compressor running 10 hours a day it uses 10.00 kWh a day. At the Texas rate of 15.5¢/kWh that's $0.15 an hour, $1.55 a day and $48.05 for a 31-day month.
Reference
Reference table
Window AC cost per month at 18.4¢/kWh (US average), 30 days
| 4 h | 8 h | 12 h | |
|---|---|---|---|
| 5,000 BTU (CEER 10) | $11.04 | $22.08 | $33.12 |
| 8,000 BTU (CEER 11) | $16.06 | $32.12 | $48.17 |
| 12,000 BTU (CEER 11) | $24.09 | $48.17 | $72.26 |
Questions
FAQ
How many watts does a 5,000, 8,000 or 12,000 BTU window AC use?
Divide the BTU by the CEER. A 5,000 BTU unit with CEER 10 uses 500 W; an 8,000 BTU unit with CEER 11 uses about 727 W; a 12,000 BTU unit with CEER 11 uses about 1,091 W while the compressor runs.
How much does a window AC cost per month?
At the US average rate of 18.4¢/kWh, an 8,000 BTU unit (CEER 11) with 8 compressor hours a day costs an estimated $32.12 a month. In Arizona at 15.0¢/kWh, a 5,000 BTU unit (CEER 10) running 12 hours a day comes to $27.00.
Is a window AC cheaper than central air?
Per hour, yes: a window unit draws hundreds of watts, and a 3-ton central system draws about 2,500 W or more. At the US average rate and 8 compressor hours a day, the examples on our two calculators come to $32.12 a month for an 8,000 BTU window unit and $113.55 for a 3-ton, SEER2 14 central system. The window unit cools one room, though. Check the Central Air calculator for your system.
Does Eco mode save money?
On most units, Eco (or Energy Saver) mode turns the fan off when the compressor stops instead of running it all the time. The compressor is where the watts go, so the effect shows up as fewer compressor hours. Enter a lower hours figure in Compare mode to see what it's worth at your rate.
What CEER should I look for?
Higher is cheaper to run. The federal minimum since 2023 is a CEER of 11 for an 8,000 BTU unit. Use Compare mode with CEER 11 vs a higher number to see the monthly difference in your state.
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