A 3-ton central air conditioner in Rhode Island costs about $93.38 in July and $230 a year at 29.05¢/kWh; an 8,000 BTU window unit about $18.26 in July.
At 29.05¢/kWh — Rhode Island average, Jan–Aug 2026 (EIA). That is 60% above the U.S. average of 18.19¢.
| Efficiency | Per year | vs yours |
|---|---|---|
| SEER2 13.4 (min · North) | $230 | — |
| SEER2 14.3 (min · South) | $215 | −$14.45 |
| SEER2 15.2 (ENERGY STAR) | $202 | −$27.19 |
| SEER2 17 (ES average) | $181 | −$48.62 |
| Month | Full-load hours | 3-ton central | 8,000 BTU window |
|---|---|---|---|
| May | 4 | $3.37 | $0.66 |
| June | 41 | $31.77 | $6.21 |
| July | 120 | $93.38 | $18.26 |
| August | 104 | $81.35 | $15.91 |
| September | 24 | $18.77 | $3.67 |
| October | 1 | $0.96 | $0.19 |
DOE's room-AC test assumes 750 full-load hours a year for a typical U.S. home. We scale it by Rhode Island's population-weighted cooling degree days (477 ÷ 1,216) and spread it over the months the same way: 294 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. × 294 h = 790 kWh × 29.05¢ = $230.
The full method, material data and tips are on the main air conditioner cost calculator page.