Window AC vs Central Air: Monthly Cost
Enter how many window units you'd run and their size, and the size of the central system, and see which costs less per month in your state, and by how much.
Window AC vs central air
C05Scenario 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) ·
Window units cost less per month by
2 window units: $64.23 a month · central air: $113.55 a month.
- Window AC(s) per month
- $64.23
- Central air per month
- $113.55
- Difference (central − window)
- $49.32
Estimate. Formula and sources are under “How it works”. Change any input; the result updates as you type.
2026 note: The federal 25C and 25D tax credits ended for installations after Dec 31, 2025. Our numbers use 2026 rules. State rebates, HEAR/HOMES programs and utility programs may still apply.
Formula
How it works
- Window units per month = number of units × BTU ÷ CEER ÷ 1,000 × hours per day × 30 × rate
- Central air per month = tons × 12,000 ÷ SEER2 ÷ 1,000 × hours per day × 30 × rate
Both assume the compressors run the hours you enter for 30 days. The answer depends on how much of the house you cool. Cooling two bedrooms with window units costs less than cooling the whole house with central air. Cooling the whole house with enough window units to match costs more, because a window unit turns fewer BTU into cold air per watt than a modern central system.
Sources: CEER: DOE room air conditioner test procedure (10 CFR 430). SEER2: AHRI 210/240-2023. Electricity rate: EIA Electric Power Monthly table 5.6.A.
Worked example
A worked example
Three 10,000 BTU window units at CEER 12 draw 2.5 kW together. Running 12 hours a day for 30 days at the Texas rate of 15.5¢/kWh, they cost an estimated $139.50 a month. A 4-ton central system at SEER2 16 draws 3 kW and costs $167.40 for the same hours. The window units come out $27.90 a month cheaper, while cooling 30,000 BTU/h of rooms instead of 48,000.
Reference
By state, at the default inputs
Window units cost less per month by, with this page's default inputs and each state's reference prices (EIA reference 2025–26, data as of 2026-09-26).
| US average | $49.32 | 18.4¢/kWh |
|---|---|---|
| Alabama | $41.55 | 15.5¢/kWh |
| Alaska | $67.01 | 25.0¢/kWh |
| Arizona | $40.21 | 15.0¢/kWh |
| Arkansas | $34.85 | 13.0¢/kWh |
| California | $85.78 | 32.0¢/kWh |
| Colorado | $42.89 | 16.0¢/kWh |
| Connecticut | $80.42 | 30.0¢/kWh |
| Delaware | $45.57 | 17.0¢/kWh |
| District of Columbia | $50.93 | 19.0¢/kWh |
| Florida | $40.21 | 15.0¢/kWh |
| Georgia | $38.87 | 14.5¢/kWh |
| Hawaii | $112.58 | 42.0¢/kWh |
| Idaho | $32.17 | 12.0¢/kWh |
| Illinois | $45.57 | 17.0¢/kWh |
| Indiana | $41.55 | 15.5¢/kWh |
| Iowa | $36.19 | 13.5¢/kWh |
| Kansas | $38.87 | 14.5¢/kWh |
| Kentucky | $34.85 | 13.0¢/kWh |
| Louisiana | $33.51 | 12.5¢/kWh |
| Maine | $69.69 | 26.0¢/kWh |
| Maryland | $50.93 | 19.0¢/kWh |
| Massachusetts | $77.74 | 29.0¢/kWh |
| Michigan | $52.27 | 19.5¢/kWh |
| Minnesota | $41.55 | 15.5¢/kWh |
| Mississippi | $36.19 | 13.5¢/kWh |
| Missouri | $34.85 | 13.0¢/kWh |
| Montana | $34.85 | 13.0¢/kWh |
| Nebraska | $32.17 | 12.0¢/kWh |
| Nevada | $40.21 | 15.0¢/kWh |
| New Hampshire | $72.37 | 27.0¢/kWh |
| New Jersey | $58.97 | 22.0¢/kWh |
| New Mexico | $40.21 | 15.0¢/kWh |
| New York | $67.01 | 25.0¢/kWh |
| North Carolina | $38.87 | 14.5¢/kWh |
| North Dakota | $30.83 | 11.5¢/kWh |
| Ohio | $44.23 | 16.5¢/kWh |
| Oklahoma | $34.85 | 13.0¢/kWh |
| Oregon | $38.87 | 14.5¢/kWh |
| Pennsylvania | $49.59 | 18.5¢/kWh |
| Rhode Island | $77.74 | 29.0¢/kWh |
| South Carolina | $40.21 | 15.0¢/kWh |
| South Dakota | $34.85 | 13.0¢/kWh |
| Tennessee | $36.19 | 13.5¢/kWh |
| Texas | $41.55 | 15.5¢/kWh |
| Utah | $32.17 | 12.0¢/kWh |
| Vermont | $58.97 | 22.0¢/kWh |
| Virginia | $41.55 | 15.5¢/kWh |
| Washington | $32.17 | 12.0¢/kWh |
| West Virginia | $41.55 | 15.5¢/kWh |
| Wisconsin | $46.91 | 17.5¢/kWh |
| Wyoming | $33.51 | 12.5¢/kWh |
Questions
FAQ
Is it cheaper to run window units or central air?
For a few rooms, window units. At the US average rate and 8 hours a day, two 8,000 BTU units cost an estimated $64.23 a month and a 3-ton central system $113.55. In New York, one 6,000 BTU unit costs $24.55 a month against $96.43 for 2.5-ton central air.
How many window units equal a central AC?
On cost, at the default sizes (8,000 BTU, CEER 11 vs 3 tons, SEER2 14): three window units cost $96.35 a month, still $17.21 less than central. Four cost $128.47, $14.91 more. So the crossover is between three and four units.
Are window units less efficient than central air?
Per BTU, usually. A CEER 11 window unit draws about 727 W per 8,000 BTU/h; a SEER2 14 central system draws about 571 W for the same 8,000 BTU/h. The window unit wins only because you cool fewer rooms.
Does closing off rooms with central air save the same?
Not reliably. A central system still cools the ducts and the whole air loop, and closing too many vents can hurt airflow. If you only need a few rooms cool, window units or a mini split are the direct way.
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