A 3-ton central air conditioner in Wisconsin costs about $58.71 in July and $158 a year at 19.05¢/kWh; an 8,000 BTU window unit about $11.48 in July.
At 19.05¢/kWh — Wisconsin average, Jan–Aug 2026 (EIA). That is 5% above the U.S. average of 18.19¢.
| Efficiency | Per year | vs yours |
|---|---|---|
| SEER2 13.4 (min · North) | $158 | — |
| SEER2 14.3 (min · South) | $148 | −$9.97 |
| SEER2 15.2 (ENERGY STAR) | $140 | −$18.77 |
| SEER2 17 (ES average) | $125 | −$33.56 |
| Month | Full-load hours | 3-ton central | 8,000 BTU window |
|---|---|---|---|
| May | 19 | $9.79 | $1.91 |
| June | 62 | $31.88 | $6.23 |
| July | 115 | $58.71 | $11.48 |
| August | 91 | $46.72 | $9.13 |
| September | 19 | $9.79 | $1.91 |
| October | 2 | $1.26 | $0.25 |
DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Wisconsin's population-weighted cooling degree days (502 ÷ 1,216) and spread it over the months the same way: 310 hours a year. Your thermostat setting and insulation move this a lot — switch the calculator to your own hours if you know them.
3 tons = 36,000 BTU/h ÷ SEER2 13.4 = 2,687 W. × 310 h = 832 kWh × 19.05¢ = $158.
The full method, material data and tips are on the main air conditioner cost calculator page.