What size AC for Wilmington, NC? 3.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Wilmington needs

3.5 tons central AC or heat pump, about 38,400 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.2 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 tons for an average 2,000 sq ft house here, ask to see the Manual J load calculation behind it before you sign. That works out to one ton per 625 square feet in this climate. For a single room, size by the room: 19.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Wilmington International Airport (4.1 mi away). Jul is the hottest month, averaging a high of 90°F and a low of 73°F, with about 45 days a year at 90°F or more. That gives a design temperature of 95°F against 75°F inside.

What it costs to run

About 3,351 kWh a year at SEER2 14.3, or roughly $501 at North Carolina's average residential rate of 14.94¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Wilmington

Of the 38,400 BTU/hr, 14,400 comes through walls, roof and windows on a 95°F afternoon (38%), 13,000 is sun on the house (34%), 2,120 is four people and their appliances, and 8,900 is moisture the coil has to wring out of Wilmington's summer air (23%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 29,520 BTU/hr before the moisture allowance.

Other house sizes in Wilmington

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,900 BTU/hr; a 350 sq ft living room needs about 6,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,500 BTU/hr.

Month by month in Wilmington

Jul alone uses 24% of the year's cooling energy. The unit runs the equivalent of 1,249 hours a year at full output.

Wilmington against nearby cities

Of 91 North Carolina cities here, Wilmington has the 8th highest cooling load. The range runs from Boone at 21,700 BTU/hr to Lumberton at 40,200.

Where Wilmington's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Wilmington International Airport, 4.1 miles from the center of Wilmington at 23 ft above sea level. That is close enough that the station's summers are Wilmington's summers.

1 other city uses the same station and get the same climate inputs. The closest to Wilmington: Leland (9 mi away, 9 mi from the station). Wilmington sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Wilmington in late July

At 34.21°N, the noon sun on 21 July stands 76.2° above the horizon over Wilmington and the day runs 13 h 57 min from sunrise to sunset. A lower noon sun puts more of the day's heat on east and west walls than on the roof, which is why shading west glass pays off here. Shorter days give the house a longer night to shed the day's heat.

125,284 people live in Wilmington, the 8th largest of the 91 North Carolina cities sized on this site. Coordinates used: 34.2092, -77.8858.

Wilmington AC sizing questions