What size AC for Aiken, SC? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 40,400 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.4 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 594 square feet in this climate. For a single room, size by the room: 20.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Aiken 2 E (2.1 mi away). Jul is the hottest month, averaging a high of 93.4°F and a low of 70.4°F, with about 81 days a year at 90°F or more. That gives a design temperature of 100°F against 75°F inside.

What it costs to run

About 3,137 kWh a year at SEER2 14.3, or roughly $499 at South Carolina's average residential rate of 15.9¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Aiken

Of the 40,400 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (45%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 7,300 is moisture the coil has to wring out of Aiken'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 33,120 BTU/hr before the moisture allowance.

Other house sizes in Aiken

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,000 BTU/hr; a 350 sq ft living room needs about 7,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,100 BTU/hr.

Month by month in Aiken

Jul alone uses 25% of the year's cooling energy. The unit runs the equivalent of 1,110 hours a year at full output.

Aiken against nearby cities

Of 42 South Carolina cities here, Aiken has the 16th highest cooling load. The range runs from Gaffney at 32,300 BTU/hr to Columbia at 43,100.

Where Aiken's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Aiken 2 E, 2.1 miles from the center of Aiken at 512 ft above sea level. That is close enough that the station's summers are Aiken's summers.

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

The sun over Aiken in late July

At 33.53°N, the noon sun on 21 July stands 76.9° above the horizon over Aiken and the day runs 13 h 54 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.

32,694 people live in Aiken, the 17th largest of the 42 South Carolina cities sized on this site. Coordinates used: 33.5316, -81.7251.

Aiken AC sizing questions