A 3-ton central air conditioner in Tennessee costs about $82.28 in July and $289 a year at 13.80¢/kWh; an 8,000 BTU window unit about $17.17 in July.
At 13.80¢/kWh — Tennessee average, Jan–Aug 2026 (EIA). That is 24% below the U.S. average of 18.19¢.
| Efficiency | Per year | vs yours |
|---|---|---|
| SEER2 13.4 (min · North) | $308 | +$19.41 |
| SEER2 14.3 (min · South) | $289 | — |
| SEER2 15.2 (ENERGY STAR) | $272 | −$17.12 |
| SEER2 17 (ES average) | $243 | −$45.91 |
| Month | Full-load hours | 3-ton central | 8,000 BTU window |
|---|---|---|---|
| January | 1 | $0.43 | $0.09 |
| March | 7 | $2.36 | $0.49 |
| April | 10 | $3.64 | $0.76 |
| May | 68 | $23.78 | $4.96 |
| June | 163 | $56.57 | $11.80 |
| July | 237 | $82.28 | $17.17 |
| August | 211 | $73.28 | $15.29 |
| September | 109 | $37.71 | $7.87 |
| October | 23 | $8.14 | $1.70 |
| November | 1 | $0.43 | $0.09 |
DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Tennessee's population-weighted cooling degree days (1,349 ÷ 1,216) and spread it over the months the same way: 832 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 14.3 = 2,517 W. × 832 h = 2,095 kWh × 13.80¢ = $289.
The full method, material data and tips are on the main air conditioner cost calculator page.