Winter design temperature by city
The cold day you design for, in 169 U.S. cities across every state — and how to read it against a heat pump’s certified capacity.
Checked against the sources below on October 7, 2026
The short answer
The winter design temperature is the outdoor temperature a location stays above for 99% of the hours in a year. It is the cold day you design heating for — not the record low. Below are the figures for 169 U.S. cities across all 50 states, D.C. and Puerto Rico; the coldest on the list is Fargo, North Dakota, at -14.5°F.
The country at a glance
Each tile shows the 99% winter design temperature of the coldest listed city in that state. It is a way to see the spread, not a number for the whole state — Prescott (20.7°F) and Phoenix (41.6°F) are both Arizona.
What each column means
| Column | What it is | How often it is worse |
|---|---|---|
| Winter 99% | Dry-bulb temperature the location stays above 99% of the hours in a year. The usual heating design condition. | about 88 h / year |
| Winter 99.6% | The same idea, stricter: stays above it 99.6% of the hours. Used where running short of heat is not acceptable. | about 35 h / year |
| Summer 0.4% | Dry-bulb temperature exceeded only 0.4% of the hours in a year. A cooling design condition. | about 35 h / year |
| Extreme low | The manual’s “annual extreme daily-mean dry-bulb, minimum”. A reminder that there are days colder than the design day — it is not the all-time record. | — |
A year has 8,760 hours: 1% of that is 87.6 hours, 0.4% is 35 hours.
All 169 cities
169 cities · all temperatures in °F
| City | Winter 99% | Winter 99.6% | Summer 0.4% | Extreme low | Elevation |
|---|---|---|---|---|---|
| Birmingham, AlabamaBirmingham Municipal AP | 24.8° | 20.5° | 95.5° | 12.9° | 630 ft |
| Montgomery, AlabamaMontgomery Dannelly Fld | 27.6° | 24.3° | 96.8° | 17° | 203 ft |
| Tuscaloosa, AlabamaTuscaloosa Regional AP | 26.2° | 21.9° | 97° | 14.8° | 187 ft |
| Tuskegee, AlabamaTuskegee AP | 27.6° | 23.5° | 93.9° | 16.3° | 195 ft |
| Anchorage, AlaskaAnchorage Intl AP | -4.8° | -9.3° | 71.5° | -14.1° | 131 ft |
| Phoenix, ArizonaPhoenix Sky Harbor Intl AP | 41.6° | 38.7° | 110.3° | 34.2° | 1,106 ft |
| Prescott, ArizonaErnest A Love Fld | 20.7° | 17.7° | 94.4° | 10.4° | 5,052 ft |
| Tucson, ArizonaTucson Intl AP | 34.3° | 31.6° | 106° | 26.1° | 2,556 ft |
| Fayetteville, ArkansasFayetteville Drake Fld | 16.2° | 10° | 95.1° | 3.5° | 1,260 ft |
| Little Rock, ArkansasLittle Rock AFB | 21.7° | 17.5° | 99.5° | 9.6° | 312 ft |
| N. Little Rock, ArkansasNorth Little Rock/ Adams Fld | 23.3° | 18.5° | 95.4° | 13.2° | 568 ft |
| Fresno, CaliforniaFresno Air Terminal | 33.7° | 31.4° | 103.5° | 28.1° | 328 ft |
| Livermore, CaliforniaLivermore Municipal AP | 33.5° | 30.2° | 99° | 26.5° | 397 ft |
| Loma Linda, CaliforniaMarch AFB/ Riverside | 35.6° | 32.1° | 100.2° | 27.5° | 1,535 ft |
| Long Beach, CaliforniaLong Beach/LB Airport | 43.6° | 41.3° | 91.1° | 36° | 39 ft |
| Los Angeles, CaliforniaLos Angeles Intl AP | 46.4° | 44.5° | 83.7° | 39.7° | 325 ft |
| Menlo Park, CaliforniaNorman Y Mineta San Jose Intl AP | 37.7° | 35.8° | 91.6° | 31.8° | 49 ft |
| Palo Alto, CaliforniaNorman Y Mineta San Jose Intl AP | 37.7° | 35.8° | 91.6° | 31.8° | 49 ft |
| Sacramento/ Mather, CaliforniaSacramento Mather | 32° | 29.7° | 101.6° | 25.8° | 95 ft |
| San Diego, CaliforniaSan Diego Lindbergh Fld | 46.8° | 44.8° | 83.1° | 41° | 30 ft |
| San Francisco, CaliforniaSan Francisco Intl AP | 41.4° | 39.1° | 82.8° | 35.4° | 20 ft |
| Sepulveda, CaliforniaBurbank/ Glendale AP | 41° | 38.6° | 97.7° | 33.2° | 732 ft |
| Denver, ColoradoDenver Stapleton Intl AP | 5.1° | -1.4° | 93.9° | -10.4° | 5,289 ft |
| Ft. Lyon, ColoradoLa Junta Municipal AP | 7.8° | 1.6° | 99.6° | -5.4° | 4,216 ft |
| Grand Junction, ColoradoGrand Junction/ Walk | 10.2° | 5.1° | 97.7° | 0.1° | 4,839 ft |
| Newington, ConnecticutHartford/ Brainard Fld | 12.2° | 8.5° | 90.7° | 3.2° | 20 ft |
| West Haven, ConnecticutMeriden Markham Municipal AP | 9.8° | 5.2° | 90.6° | -1.5° | 105 ft |
| Wilmington, DelawareWilmington New Castle Co AP | 17.3° | 13.3° | 91.9° | 7.7° | 79 ft |
| Washington DC, District Of ColumbiaWashington/ National DC Reagan AP | 20.7° | 17.3° | 94.5° | 12° | 66 ft |
| Bay Pines, FloridaSt. Petersburg Clearwater AP | 45.4° | 42.4° | 92.1° | 34.4° | 10 ft |
| Gainesville, FloridaGainesville Regional AP | 33.4° | 29.6° | 93.4° | 23.4° | 164 ft |
| Lake City, FloridaGainesville Regional AP | 33.4° | 29.6° | 93.4° | 23.4° | 164 ft |
| Miami, FloridaMiami Intl AP | 51.9° | 47.6° | 91.8° | 41.6° | 30 ft |
| Orlando, FloridaOrlando Jetport AP | 42.3° | 37.8° | 93.8° | 31.3° | 105 ft |
| Tampa, FloridaTampa Intl AP | 42.9° | 38.8° | 92.6° | 32.1° | 10 ft |
| West Palm, FloridaWest Palm Beach | 48° | 43.9° | 91.4° | 37.5° | 20 ft |
| Atlanta, GeorgiaAtlanta Hartsfield Intl AP | 26.4° | 21.5° | 93.9° | 14.1° | 1,027 ft |
| Augusta, GeorgiaAugusta Bush Fld | 26.1° | 22.5° | 97.3° | 16.2° | 148 ft |
| Decatur, GeorgiaAtlanta Hartsfield Intl AP | 26.4° | 21.5° | 93.9° | 14.1° | 1,027 ft |
| Dublin, GeorgiaDublin AP | 27.4° | 23.9° | 96.9° | 17.1° | 215 ft |
| Honolulu, HawaiiHonolulu Intl AP | 63.9° | 62° | 89.9° | 58.4° | 16 ft |
| Boise, IdahoBoise Air Terminal | 15.5° | 8.7° | 98.6° | 3.5° | 2,867 ft |
| Chicago Lakeside Clinic, IllinoisChicago O’Hare Intl AP | 3.7° | -1.5° | 91.4° | -8° | 673 ft |
| Chicago W. Side, IllinoisChicago O’Hare Intl AP | 3.7° | -1.5° | 91.4° | -8° | 673 ft |
| Danville, IllinoisUniversity of Illinois | 4.2° | -0.5° | 92° | -9.7° | 764 ft |
| Hines, IllinoisChicago Midway AP | 5.4° | 0.2° | 91.5° | -6.3° | 617 ft |
| Marion, IllinoisMt. Vernon (AWOS) | 11.5° | 5.4° | 93.4° | -5.9° | 479 ft |
| Ft Wayne, IndianaFt. Wayne Intl AP | 5° | -0.7° | 90.8° | -6.7° | 827 ft |
| Indianapolis, IndianaIndianapolis Intl AP | 8.1° | 2° | 91° | -5.3° | 807 ft |
| Marion, IndianaDelaware Co Johnson | 7.3° | 1.2° | — | -3.8° | 948 ft |
| Des Moines, IowaDes Moines Intl AP | -0.2° | -5.3° | 92.5° | -11.4° | 965 ft |
| Iowa City, IowaIowa City Municipal AP | 0.5° | -4.1° | 91.1° | -12.8° | 669 ft |
| Knoxville, IowaDes Moines Intl AP | -0.2° | -5.3° | 92.5° | -11.4° | 965 ft |
| Leavenworth, KansasKansas City Intl AP, MO | 7.2° | 2° | 95.8° | -4.5° | 1,024 ft |
| Topeka, KansasTopeka/ Billard Municipal AP | 8.7° | 3.1° | 97.1° | -4° | 886 ft |
| Wichita, KansasWichita/ Mid- Continent AP | 12.2° | 7.4° | 100.1° | — | 1,339 ft |
| Lexington, KentuckyLexington Bluegrass AP | 13.6° | 8.3° | 91.6° | — | 988 ft |
| Louisville, KentuckyLouisville | 15.9° | 10.2° | 93.8° | 3.2° | 489 ft |
| Alexandria, LouisianaAlexandra Intl AP | 29.3° | 27.4° | 97.2° | 21.5° | 79 ft |
| New Orleans, LouisianaNew Orleans Lakefront AP | 38.6° | 35.6° | 93.3° | 29.7° | 10 ft |
| Shreveport, LouisianaShreveport Regional AP | 28.4° | 25.2° | 98.5° | 19.3° | 259 ft |
| Togus, MaineAugusta AP | 1.3° | -3.2° | 87.5° | — | 361 ft |
| Baltimore, MarylandBaltimore- Washington Intl AP | 17.9° | 14° | 94° | 6.9° | 154 ft |
| Perry Point, MarylandBaltimore- Washington Intl AP | 17.9° | 14° | 94° | 6.9° | 154 ft |
| Bedford, MassachusettsBoston Logan Intl AP | 13° | 8.1° | 90.6° | 2.8° | 30 ft |
| Brockton, MassachusettsTaunton Muni | 10.2° | 6.6° | 90.4° | 0.1° | 43 ft |
| Jamaica Plain - Boston, MassachusettsBoston Logan Intl AP | 13° | 8.1° | 90.6° | 2.8° | 30 ft |
| Leeds, MassachusettsChicopee Falls/ West | 5.1° | -0.2° | 91° | -8.8° | 246 ft |
| West Roxbury, MassachusettsBoston Logan Intl AP | 13° | 8.1° | 90.6° | 2.8° | 30 ft |
| Allen Park, MichiganDetroit Metro AP | 8° | 2.9° | 90.4° | -2.7° | 663 ft |
| Ann Arbor, MichiganAnn Arbor Municipal AP | 4.9° | 0.4° | 89.8° | -10.1° | 840 ft |
| Battle Creek, MichiganW K Kellogg AP | 7.2° | 2.5° | 89.8° | -5.6° | 938 ft |
| Detroit, MichiganDetroit Metro AP | 8° | 2.9° | 90.4° | -2.7° | 663 ft |
| Iron Mountain, MichiganIron Mountain/ Ford | -6.3° | -10.7° | 88.2° | -19° | 1,181 ft |
| Saginaw, MichiganMBS International AP | 4.6° | 0.4° | 89.9° | -5.7° | 669 ft |
| Minneapolis, MinnesotaMinneapolis/St. Paul Intl AP | -6.2° | -11.2° | 90.9° | -17.2° | 837 ft |
| St. Cloud, MinnesotaSt. Cloud Regional AP | -11.4° | -17.2° | 89.9° | -24.4° | 1,024 ft |
| Biloxi, MississippiKeesler AFB/ Biloxi | 35.1° | 30.7° | 93.5° | 22.4° | 33 ft |
| Gulfport, MississippiKeesler AFB/ Biloxi | 35.1° | 30.7° | 93.5° | 22.4° | 33 ft |
| Jackson, MississippiJackson Intl AP | 26.7° | 23.2° | 96.4° | 17.1° | 331 ft |
| Columbia, MissouriColumbia Regional AP | 8.6° | 2.8° | 94.2° | -3.8° | 899 ft |
| Kansas City, MissouriKansas City | 7.2° | 2° | 95.8° | -4.5° | 1,024 ft |
| Poplar Bluff, MissouriPoplar Bluff (AMOS) | 17.2° | 11.7° | 93.9° | 5.3° | 328 ft |
| St. Louis (JBO), MissouriSt. Louis Lambert Intl AP | 11.7° | 6.6° | 95.5° | 0.7° | 709 ft |
| Ft. Harrison, MontanaHelena Regional AP | -6.6° | -13° | 92.9° | -20.3° | 3,868 ft |
| Miles City, MontanaMiles City Municipal AP | -9.2° | -16° | 98.5° | -22.5° | 2,635 ft |
| Grand Island, NebraskaGrand Island Central NE Region | 1.1° | -4.3° | 95.7° | -11.5° | 1,857 ft |
| Lincoln, NebraskaLincoln Co | 1.5° | -3.5° | 96.9° | -10.4° | 1,188 ft |
| Omaha, NebraskaOmaha Eppley Airfield | 0.6° | -4.3° | 94.5° | -10.8° | 981 ft |
| Las Vegas, NevadaNellis AFB | 30.9° | 27.7° | 109.2° | 20.1° | 1,867 ft |
| Reno, NevadaReno/ Cannon Intl AP | 17.6° | 12.1° | 96.3° | 5.3° | 4,400 ft |
| Manchester, New HampshireManchester AP | 7.1° | 1.4° | 91.1° | -5.1° | 233 ft |
| East Orange, New JerseyNewark International AP | 16.6° | 12.3° | 94.2° | 7.5° | 30 ft |
| Lyons, New JerseyNewark International AP | 16.6° | 12.3° | 94.2° | 7.5° | 30 ft |
| Albuquerque, New MexicoAlbuquerque | 21.6° | 18.2° | 95.3° | 10.9° | 5,315 ft |
| Albany, New YorkAlbany Co AP | 3.9° | -0.9° | 89.2° | -8° | 292 ft |
| Batavia, New YorkRochester- Monroe Co | 6.9° | 2.9° | 88.7° | -2.7° | 554 ft |
| Bath, New YorkElmira Corning Regional AP | 4.7° | -0.3° | 89.9° | -9.7° | 955 ft |
| Bronx, New YorkNYC/ John F. Kennedy Intl AP | 17.8° | 13.8° | 89.8° | 8.8° | 23 ft |
| Brooklyn, New YorkNYC/ John F. Kennedy Intl AP | 17.8° | 13.8° | 89.8° | 8.8° | 23 ft |
| Buffalo, New YorkGreater Buffalo Intl AP | 7.4° | 3.6° | 86.4° | -1.8° | 705 ft |
| Canandaigua, New YorkRochester- Monroe Co | 6.9° | 2.9° | 88.7° | -2.7° | 554 ft |
| Montrose, New YorkStewart AFB | 9.5° | 4.6° | 90.2° | -2° | 492 ft |
| New York City, New YorkNYC/ John F. Kennedy Intl AP | 17.8° | 13.8° | 89.8° | 8.8° | 23 ft |
| Northport, New YorkLong Island Mac Arthur AP | 15.7° | 11.5° | 88.5° | 5.9° | 98 ft |
| St. Albans, New YorkSyracuse/ Hancock Intl AP | 4.3° | -1.2° | 89.2° | -8.7° | 417 ft |
| Syracuse, New YorkSyracuse/ Hancock Intl AP | 4.3° | -1.2° | 89.2° | -8.7° | 417 ft |
| Wappingers Falls - Castle Point Campus, New YorkDutchess Co AP | 7.5° | 1.7° | 91.4° | -5.9° | 161 ft |
| Asheville (Oteen), North CarolinaAsheville Municipal AP | 18.9° | 14.7° | 88.3° | 6.8° | 2,169 ft |
| Durham, North CarolinaRaleigh Durham Intl AP | 23.6° | 19.6° | 94.8° | 12.6° | 436 ft |
| Fayetteville, North CarolinaFort Bragg Simmons AAF | 25.8° | 21.9° | 97° | 14.3° | 243 ft |
| Salisbury, North CarolinaSmith Reynolds AP | 23.3° | 18.9° | 92.9° | 11.9° | 971 ft |
| Fargo, North DakotaFargo Hector Intl AP | -14.5° | -19.3° | 90.7° | -24.9° | 899 ft |
| Chillicothe, OhioColumbus/ Port Columbus International AP | 10.4° | 5° | 91.1° | -1° | 817 ft |
| Cincinnati, OhioCincinnati Municipal AP Lunki | 13.4° | 8.1° | 92.8° | 0.5° | 499 ft |
| Cleveland, OhioCleveland Hopkins Intl AP | 9.7° | 4.1° | 89.7° | -2° | 804 ft |
| Columbus, OhioColumbus/ Port Columbus International AP | 10.4° | 5° | 91.1° | -1° | 817 ft |
| Dayton, OhioDayton Intl AP | 8.1° | 2° | 90.4° | -4.6° | 1,004 ft |
| Muskogee, OklahomaMuskogee | 19.2° | 16.4° | 99.4° | 8.8° | 610 ft |
| Oklahoma City, OklahomaOklahoma City Will Rogers World AP | 18.9° | 14.1° | 99.6° | 7.5° | 1,306 ft |
| Portland, OregonPortland Intl AP | 29.5° | 25.2° | 91.4° | 20.9° | 108 ft |
| Roseburg, OregonRoseburg AP | 30° | 27.6° | 93.2° | 22° | 509 ft |
| White City, OregonMedford-Jackson Intl AP | 26.1° | 23.1° | 99.2° | 17.9° | 1,329 ft |
| Altoona, PennsylvaniaAltoona Blair Co AP | 10° | 5.9° | 88.3° | -0.7° | 1,470 ft |
| Butler, PennsylvaniaButler Co (AWOS) | 8.8° | 3.2° | 88.1° | -2.2° | 1,247 ft |
| Coatesville, PennsylvaniaLancaster | 15.5° | 10.1° | 90.9° | 4.7° | 404 ft |
| Erie, PennsylvaniaErie Intl AP | 10.4° | 6.8° | 86.7° | 1.2° | 738 ft |
| Lebanon, PennsylvaniaHarrisburg Capital City AP | 15.4° | 10.7° | 92.5° | 5.8° | 348 ft |
| Philadelphia, PennsylvaniaPhiladelphia Intl AP | 18° | 13.8° | 93.4° | 9° | 30 ft |
| Pittsburgh, PennsylvaniaGreater Pittsburgh Intl AP | 9.9° | 5.2° | 89.7° | -1.1° | 1,204 ft |
| Wilkes-Barre, PennsylvaniaWilkes-Barre Scranton Intl AP | 9.1° | 4.4° | 89.3° | -1.1° | 961 ft |
| San Juan, Puerto RicoSan Juan Intl AP | 70.4° | 69.4° | 91° | 67.7° | 13 ft |
| Providence, Rhode IslandProvidence/TF Green State | 12.9° | 8.5° | 90.1° | 2.9° | 62 ft |
| Charleston, South CarolinaCharleston Municipal AP | 30.4° | 27.3° | 94.3° | 20.8° | 49 ft |
| Columbia, South CarolinaColumbia Metro AP | 26.5° | 22.8° | 97.2° | 16.5° | 226 ft |
| Ft. Meade, South DakotaRapid City Regional AP | -3.4° | -9.2° | 97.2° | -17° | 3,169 ft |
| Sioux Falls, South DakotaSioux Falls Foss Fld | -7.3° | -12.3° | 92.2° | -19.1° | 1,427 ft |
| Memphis, TennesseeMemphis Intl AP | 22.9° | 18.7° | 96.7° | 12.6° | 331 ft |
| Mountain Home, TennesseeBristol-Tri-City AP | 17.7° | 12.9° | 90.5° | 4.6° | 1,526 ft |
| Murfreesboro, TennesseeNashville/ Metropolis | 19.3° | 14.8° | 94.8° | 7.6° | 604 ft |
| Nashville, TennesseeNashville Intl AP | 19.3° | 14.8° | 94.8° | 7.6° | 604 ft |
| Amarillo, TexasAmarillo Intl AP | 15.6° | 9.8° | 97.3° | 2.4° | 3,606 ft |
| Big Spring, TexasSan Angelo/ Mathis | 25.9° | 21.9° | 100.4° | 14.7° | 1,893 ft |
| Bonham, TexasCox Field, Paris, TX | 25.2° | 20.8° | 99.3° | 13.6° | 548 ft |
| Dallas, TexasDallas-Fort Worth Intl AP | 27.3° | 23° | 100.5° | 17.5° | 597 ft |
| Harlingen, TexasValley International AP | 40.8° | 36.7° | 98.8° | 31.5° | 36 ft |
| Houston, TexasHouston Bush InterContinental AP | 33.8° | 30.3° | 97.2° | 25.6° | 105 ft |
| Kerrville, TexasSan Antonio Intl AP | 32.7° | 29.2° | 99° | 23° | 810 ft |
| San Antonio, TexasSan Antonio Intl AP | 32.7° | 29.2° | 99° | 23° | 810 ft |
| Temple, TexasDraughon-Miller Central Regional AP | 28° | 25° | 99.7° | 19.2° | 682 ft |
| Waco, TexasWaco Regional AP | 28.1° | 24.6° | 100.5° | 18.8° | 509 ft |
| Salt Lake City, UtahSalt Lake City Intl AP | 14.2° | 9.6° | 97.7° | 2.9° | 4,226 ft |
| White River Junction, VermontEdward F. Knapp State AP | -5.5° | -10.2° | 85.1° | -17.7° | 1,122 ft |
| Hampton, VirginiaNorfolk Intl AP | 26.2° | 22.5° | 93.7° | 17.4° | 30 ft |
| Richmond, VirginiaDinwiddie Co | 19.3° | 16.1° | 97.3° | 6.2° | 194 ft |
| Salem, VirginiaRoanoke Regional AP | 19.6° | 15.7° | 92.3° | 8.4° | 1,175 ft |
| Seattle, WashingtonSeattle-Tacoma International AP | 29.6° | 25.2° | 85.3° | 21.2° | 433 ft |
| Spokane, WashingtonFairchild AFB | 11.7° | 6.8° | 92.9° | — | 2,461 ft |
| Vancouver, WashingtonPortland Intl AP | 29.5° | 25.2° | 91.4° | 20.9° | 108 ft |
| Walla Walla, WashingtonWalla Walla City Co AP | 18° | 10.4° | 98.7° | 8.3° | 1,204 ft |
| Beckley, West VirginiaBeckley Raleigh Co MEM AP | 11.5° | 6.8° | 84.8° | -1.5° | 2,513 ft |
| Clarksburg, West VirginiaElkins-Randolph Co Regional AP | 7.5° | 1.3° | 87° | -10.2° | 1,978 ft |
| Huntington, West VirginiaHuntington Tri- State AP | 15.5° | 10.1° | 91.9° | 2° | 837 ft |
| Martinsburg, West VirginiaEastern WV Regional AP | 15.8° | 11.5° | 93.1° | 2.4° | 535 ft |
| Madison, WisconsinMadison Dane Co Regional AP | -1.6° | -7° | 89.6° | -13.9° | 866 ft |
| Milwaukee, WisconsinMilwaukee Mitchell Intl AP | 3.2° | -1.4° | 90° | -7.9° | 692 ft |
| Tomah, WisconsinLa Crosse Municipal AP | -4.5° | -9.3° | 91.7° | -16.2° | 656 ft |
| Cheyenne, WyomingCheyenne/ Warren AFB | 2.9° | -3.7° | 89.7° | -12.5° | 6,142 ft |
| Sheridan, WyomingSheridan Co AP | -4.1° | -10.7° | 95.3° | -19.3° | 3,967 ft |
Your city is not on the list?
These are the cities where the Department of Veterans Affairs has a facility — it is not a ZIP-code table. Use the closest listed city with a similar climate and elevation, and check whether your jurisdiction or your load-calculation procedure names a specific source for design temperatures. A few cells in the printed table are plainly typos; where a value failed a physical sanity check it is shown here as “—” rather than guessed.
Reading it against a heat pump
ENERGY STAR publishes the certified heating capacity of each indoor/outdoor pair at 47°F, 17°F and, for most pairs, 5°F. On its own, a capacity at 5°F answers nothing. Next to your design temperature it becomes the question a customer actually asks: what does this heat pump put out on the cold day here?
- If your design temperature sits at one of the certified points, that is the number.
- If it sits between two points and the capacity falls as it gets colder, the capacity on your design day is between the two certified values.
- If it sits below 5°F, there is no certified point down there. The manufacturer’s extended performance data is the only source.
Variable-speed units break the straight line
On many variable-capacity pairs the certified capacity at 5°F is higher than at 47°F. That is not a data error: the 47°F point is certified at nominal compressor speed and the cold points at maximum speed. Drawing a line between points measured at different speeds invents a curve that does not exist — read the two certified points as they are.
All of this is the capacity of the equipment. What the house needs on that day is a load calculation (ACCA Manual J is the residential standard), and that is a different number from a different procedure.
Sources
- HVAC Design Manual, U.S. Department of Veterans Affairs — Chapter 7, Table 7-1 “Climatic Conditions” — November 1, 2017, revised March 1, 2024. A work of the U.S. federal government.
- VA Technical Information Library — Design Manuals — where the current revision is published
Federal rules change. This page reports what the sources said on the date above; the source is the authority, and state or local rules can be stricter. It is reference material, not legal advice and not installation guidance.