A 3-ton central air conditioner in Vermont costs about $48.38 in July and $109 a year at 23.93¢/kWh; an 8,000 BTU window unit about $9.46 in July.
At 23.93¢/kWh — Vermont average, Jan–Aug 2026 (EIA). That is 32% above the U.S. average of 18.19¢.
| Efficiency | Per year | vs yours |
|---|---|---|
| SEER2 13.4 (min · North) | $109 | — |
| SEER2 14.3 (min · South) | $103 | −$6.89 |
| SEER2 15.2 (ENERGY STAR) | $96.48 | −$12.96 |
| SEER2 17 (ES average) | $86.26 | −$23.18 |
| Month | Full-load hours | 3-ton central | 8,000 BTU window |
|---|---|---|---|
| May | 7 | $4.76 | $0.93 |
| June | 26 | $16.65 | $3.26 |
| July | 75 | $48.38 | $9.46 |
| August | 54 | $34.89 | $6.82 |
| September | 7 | $4.76 | $0.93 |
DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Vermont's population-weighted cooling degree days (276 ÷ 1,216) and spread it over the months the same way: 170 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. × 170 h = 457 kWh × 23.93¢ = $109.
The full method, material data and tips are on the main air conditioner cost calculator page.