The right size matters more than the brand. An air conditioner that is too big leaves the house clammy; a heat pump that is too small leans on expensive backup heat. These calculators size each type of equipment for your home and climate.
All sizing calculators use the IECC climate zones. Choosing your state sets a typical zone, which you can change if you live in a mountain area or a different part of a large state.
| Zone | Examples | Winter design | Summer design |
|---|---|---|---|
| Hot · IECC 1–2 | Florida, south Texas, Arizona | ≈ 35–40 °F | ≈ 95 °F |
| Warm · IECC 3 | Georgia, Dallas, southern California | ≈ 25–28 °F | ≈ 95 °F |
| Mixed · IECC 4 | Tennessee, Virginia, Missouri | ≈ 15 °F | ≈ 92 °F |
| Cold · IECC 5 | Illinois, Ohio, Colorado | ≈ 2–5 °F | ≈ 90 °F |
| Very cold · IECC 6–7 | Minnesota, Wisconsin, Maine | ≈ −10 °F | ≈ 87 °F |