What size AC for Shelby, NC? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 34,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 21% more than this climate needs. An oversized unit cools the air fast, shuts off before it pulls moisture out, and leaves the house cold and clammy.

If a contractor quotes you more than 3 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 690 square feet in this climate. For a single room, size by the room: 17.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Shelby 2 Nw (2 mi away). Jul is the hottest month, averaging a high of 90.6°F and a low of 65.9°F, with about 43 days a year at 90°F or more. That gives a design temperature of 96°F against 75°F inside.

What it costs to run

About 2,028 kWh a year at SEER2 14.3, or roughly $303 at North Carolina's average residential rate of 14.94¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Shelby

Of the 34,800 BTU/hr, 15,120 comes through walls, roof and windows on a 96°F afternoon (43%), 13,000 is sun on the house (37%), 2,120 is four people and their appliances, and 4,500 is moisture the coil has to wring out of Shelby's summer air (13%).

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 30,240 BTU/hr before the moisture allowance.

Other house sizes in Shelby

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,400 BTU/hr.

Month by month in Shelby

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 834 hours a year at full output.

Shelby against nearby cities

Of 91 North Carolina cities here, Shelby has the 71st highest cooling load. The range runs from Boone at 21,700 BTU/hr to Lumberton at 40,200.

Where Shelby's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Shelby 2 Nw, 2 miles from the center of Shelby at 820 ft above sea level. That is close enough that the station's summers are Shelby's summers.

No other city in this set uses Shelby 2 Nw, so this sizing is Shelby's alone.

The sun over Shelby in late July

At 35.29°N, the noon sun on 21 July stands 75.1° above the horizon over Shelby and the day runs 14 h 02 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.

22,778 people live in Shelby, the 45th largest of the 91 North Carolina cities sized on this site. Coordinates used: 35.2904, -81.5456.

Shelby AC sizing questions