A 3-ton central air conditioner in Pennsylvania costs about $82.63 in July and $231 a year at 21.13¢/kWh; an 8,000 BTU window unit about $16.16 in July.
At 21.13¢/kWh — Pennsylvania average, Jan–Aug 2026 (EIA). That is 16% above the U.S. average of 18.19¢.
| Efficiency | Per year | vs yours |
|---|---|---|
| SEER2 13.4 (min · North) | $231 | — |
| SEER2 14.3 (min · South) | $217 | −$14.57 |
| SEER2 15.2 (ENERGY STAR) | $204 | −$27.41 |
| SEER2 17 (ES average) | $182 | −$49.01 |
| Month | Full-load hours | 3-ton central | 8,000 BTU window |
|---|---|---|---|
| May | 23 | $13.30 | $2.60 |
| June | 77 | $43.77 | $8.56 |
| July | 146 | $82.63 | $16.16 |
| August | 120 | $67.92 | $13.28 |
| September | 37 | $21.01 | $4.11 |
| October | 4 | $2.45 | $0.48 |
DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Pennsylvania's population-weighted cooling degree days (661 ÷ 1,216) and spread it over the months the same way: 408 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. × 408 h = 1,095 kWh × 21.13¢ = $231.
The full method, material data and tips are on the main air conditioner cost calculator page.