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

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

3.5 tons central AC or heat pump, about 38,700 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 621 square feet in this climate. For a single room, size by the room: 19.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Concord (4.3 mi away). Jul is the hottest month, averaging a high of 91.8°F and a low of 68.7°F, with about 61 days a year at 90°F or more. That gives a design temperature of 98°F against 75°F inside.

What it costs to run

About 2,588 kWh a year at SEER2 14.3, or roughly $387 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 Concord

Of the 38,700 BTU/hr, 16,560 comes through walls, roof and windows on a 98°F afternoon (43%), 13,000 is sun on the house (34%), 2,120 is four people and their appliances, and 7,000 is moisture the coil has to wring out of Concord's summer air (18%).

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 31,680 BTU/hr before the moisture allowance.

Other house sizes in Concord

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 6,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,600 BTU/hr.

Month by month in Concord

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 957 hours a year at full output.

Concord against nearby cities

Of 91 North Carolina cities here, Concord has the 3rd highest cooling load. The range runs from Boone at 21,700 BTU/hr to Lumberton at 40,200.

Where Concord's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Concord, 4.3 miles from the center of Concord at 670 ft above sea level. That is close enough that the station's summers are Concord's summers.

1 other city uses the same station and get the same climate inputs. The closest to Concord: Kannapolis (6 mi away, 6.6 mi from the station). Concord sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Concord in late July

At 35.39°N, the noon sun on 21 July stands 75.0° above the horizon over Concord and the day runs 14 h 03 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.

112,395 people live in Concord, the 10th largest of the 91 North Carolina cities sized on this site. Coordinates used: 35.3921, -80.6355.

Concord AC sizing questions