The short answer
A 3-ton central air conditioner (SEER2 14.3) costs about 46 cents an hour to run at the U.S. average electricity rate of 18.31¢ per kWh (July 2026). Running 8 hours a day, that's about $110.63 a month, from $76.85 in Louisiana to $290.01 in Hawaii.
The same AC in every state
A 36,000 BTU AC at 14.3 SEER2, running 8 hours a day for 30 days, at each state's average residential rate (July 2026).
| Alabama | $99.09 | $0.41 | 16.40¢ |
|---|---|---|---|
| Alaska | $174.19 | $0.73 | 28.83¢ |
| Arizona | $92.93 | $0.39 | 15.38¢ |
| Arkansas | $86.58 | $0.36 | 14.33¢ |
| California | $203.07 | $0.85 | 33.61¢ |
| Colorado | $102.71 | $0.43 | 17.00¢ |
| Connecticut | $145.97 | $0.61 | 24.16¢ |
| Delaware | $111.66 | $0.47 | 18.48¢ |
| District of Columbia | $152.32 | $0.63 | 25.21¢ |
| Florida | $90.81 | $0.38 | 15.03¢ |
| Georgia | $98.30 | $0.41 | 16.27¢ |
| Hawaii | $290.01 | $1.21 | 48.00¢ |
| Idaho | $82.96 | $0.35 | 13.73¢ |
| Illinois | $116.13 | $0.48 | 19.22¢ |
| Indiana | $101.08 | $0.42 | 16.73¢ |
| Iowa | $96.61 | $0.40 | 15.99¢ |
| Kansas | $92.26 | $0.38 | 15.27¢ |
| Kentucky | $83.44 | $0.35 | 13.81¢ |
| Louisiana | $76.85 | $0.32 | 12.72¢ |
| Maine | $195.82 | $0.82 | 32.41¢ |
| Maryland | $129.36 | $0.54 | 21.41¢ |
| Massachusetts | $184.22 | $0.77 | 30.49¢ |
| Michigan | $139.27 | $0.58 | 23.05¢ |
| Minnesota | $105.43 | $0.44 | 17.45¢ |
| Mississippi | $87.85 | $0.37 | 14.54¢ |
| Missouri | $97.22 | $0.41 | 16.09¢ |
| Montana | $90.57 | $0.38 | 14.99¢ |
| Nebraska | $83.26 | $0.35 | 13.78¢ |
| Nevada | $77.16 | $0.32 | 12.77¢ |
| New Hampshire | $160.72 | $0.67 | 26.60¢ |
| New Jersey | $152.20 | $0.63 | 25.19¢ |
| New Mexico | $97.22 | $0.41 | 16.09¢ |
| New York | $180.65 | $0.75 | 29.90¢ |
| North Carolina | $91.60 | $0.38 | 15.16¢ |
| North Dakota | $81.02 | $0.34 | 13.41¢ |
| Ohio | $117.52 | $0.49 | 19.45¢ |
| Oklahoma | $86.70 | $0.36 | 14.35¢ |
| Oregon | $96.49 | $0.40 | 15.97¢ |
| Pennsylvania | $131.23 | $0.55 | 21.72¢ |
| Rhode Island | $170.93 | $0.71 | 28.29¢ |
| South Carolina | $93.47 | $0.39 | 15.47¢ |
| South Dakota | $92.86 | $0.39 | 15.37¢ |
| Tennessee | $82.84 | $0.35 | 13.71¢ |
| Texas | $95.95 | $0.40 | 15.88¢ |
| Utah | $79.27 | $0.33 | 13.12¢ |
| Vermont | $143.50 | $0.60 | 23.75¢ |
| Virginia | $106.04 | $0.44 | 17.55¢ |
| Washington | $88.88 | $0.37 | 14.71¢ |
| West Virginia | $95.34 | $0.40 | 15.78¢ |
| Wisconsin | $115.16 | $0.48 | 19.06¢ |
| Wyoming | $86.76 | $0.36 | 14.36¢ |
How it works
The formula
kWh = watts × hours ÷ 1,000
cost = kWh × rate
Assumptions
- SEER2, EER2 and CEER are BTU of cooling per watt-hour. SEER2 is defined as a whole season's cooling divided by its electricity, so BTU ÷ SEER2 is the average draw over a season, and the monthly cost is a seasonal estimate.
- "Runs per day" is compressor time, not thermostat time. On a hot day a well-sized central AC runs about half to two thirds of the hours it's switched on.
- On the hottest afternoons a unit draws more, closer to BTU ÷ EER2 (about 20% more for a typical central unit); in mild weather it draws less. For a heat-wave month, type the EER2 into the efficiency box.
- The indoor blower adds a little: about 300 to 500 W for a central system, often counted in SEER2 already. The summer figure is 4 months.
Worked example: a 3-ton central AC
36,000 BTU, SEER2 14.3, 8 hours a day, at 18.31¢ per kWh
- Power: 36,000 ÷ 14.3 = 2,517 W
- Energy per day: 2,517 × 8 ÷ 1,000 = 20.14 kWh
- Per month: 20.14 × 30 = 604.2 kWh × $0.1831 = $110.63
- An older SEER 10 unit of the same size would cost about $158.20 a month.
Ways to cut the cost
- Set it higher when you're out. 78°F at home and 85°F away is the usual advice; each degree higher saves a few percent.
- Use a fan with it. A ceiling fan uses about 50 W and lets you set the thermostat about 4°F higher with the same comfort.
- Keep the sun out. Close blinds on sunny windows; heat through glass is a big part of the cooling load.
- Change the filter. A clogged filter makes the system run longer. Check it monthly in summer.
- Upgrade old units. Replacing a SEER 10 system with SEER2 15+ cuts cooling costs by about a third.
Questions people ask
How much does it cost to run central air conditioning?
A 3-ton central AC with a SEER2 rating of 14.3 draws about 2,517 watts on average while it runs. At the U.S. average of 18.31¢ per kWh (EIA, July 2026) that's about 46 cents an hour, or $110.63 a month if the compressor runs 8 hours a day. In Louisiana the same month costs $76.85; in Hawaii, $290.01.
How much does it cost to run a window AC unit?
A 10,000 BTU window unit with a CEER of 11 draws about 909 watts: about 17 cents an hour and $39.95 a month at 8 hours a day and the U.S. average rate.
How many watts does an air conditioner use?
Divide the BTU rating by the efficiency rating. A 36,000 BTU (3 ton) unit at SEER2 14.3 averages 36,000 ÷ 14.3 = about 2,500 watts over a cooling season. On the hottest afternoons it draws more: divide by its EER2 (often about 11 to 12) instead, about 3,000 watts. A 6,000 BTU window unit at CEER 11 uses about 550 watts.
Is it cheaper to leave the AC on all day?
Usually not. An AC uses energy to remove the heat that comes into the house, and less heat comes in when the house is warmer. Raising the thermostat while you are out, by about 7 to 10°F, saves more than it costs to cool back down. A programmable or smart thermostat does it for you.
What do SEER2, EER2 and CEER mean?
They all measure cooling per unit of electricity, in BTU per watt-hour. SEER2 is a seasonal average for central and mini-split systems (new federal tests since 2023). EER2 is the efficiency at a hot 95°F, and CEER is the rating for window and portable units. Higher is cheaper to run.