Climate zones
Climate zone determines more about equipment selection than any other single factor, and it is what generic product reviews ignore entirely. A heat pump that is excellent in Atlanta can be the wrong purchase in Minneapolis.
| Zone | Name | Design temp | HDD | CDD | Where |
|---|---|---|---|---|---|
| 1A | Very Hot – Humid | 44°F | 200 | 4,500 | South Florida, Hawaii, the US territories. |
| 2A | Hot – Humid | 32°F | 900 | 3,400 | Gulf Coast, central and north Florida, coastal Texas and Louisiana. |
| 2B | Hot – Dry | 34°F | 1,000 | 3,800 | Phoenix, Tucson, the low desert. |
| 3A | Warm – Humid | 25°F | 2,000 | 2,200 | Atlanta, Dallas, the mid-South. |
| 3B | Warm – Dry | 30°F | 1,800 | 2,400 | Southern California inland, southern Nevada, west Texas. |
| 3C | Warm – Marine | 36°F | 2,500 | 400 | California coast, San Francisco Bay Area. |
| 4A | Mixed – Humid | 14°F | 4,500 | 1,300 | Mid-Atlantic, Virginia, Tennessee, Missouri, coastal New Jersey. |
| 4B | Mixed – Dry | 18°F | 3,800 | 1,600 | New Mexico, west Texas high plains. |
| 4C | Mixed – Marine | 27°F | 4,700 | 300 | Seattle, Portland, western Washington and Oregon. |
| 5A | Cool – Humid | 2°F | 6,000 | 800 | Chicago, Boston, Denver, most of New England and the Great Lakes. |
| 5B | Cool – Dry | 3°F | 6,200 | 700 | Utah, southern Idaho, much of Colorado's Front Range. |
| 6A | Cold – Humid | -8°F | 7,500 | 500 | Minneapolis, Vermont, Maine, upstate New York, Wisconsin. |
| 6B | Cold – Dry | -10°F | 7,800 | 400 | Montana, Wyoming, high-elevation Colorado and Utah. |
| 7 | Very Cold | -20°F | 9,500 | 250 | Northern Minnesota, North Dakota, interior Maine. |
| 8 | Subarctic | -40°F | 13,000 | 100 | Interior Alaska. |