What size AC for Clemson, SC? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 35,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 20% 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 683 square feet in this climate. For a single room, size by the room: 17.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Clemson Oconee County Airport (4.1 mi away). Jul is the hottest month, averaging a high of 88.7°F and a low of 69.9°F, with about 53 days a year at 90°F or more. That gives a design temperature of 94°F against 75°F inside.

What it costs to run

About 2,456 kWh a year at SEER2 14.3, or roughly $391 at South Carolina's average residential rate of 15.9¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Clemson

Of the 35,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (39%), 13,000 is sun on the house (37%), 2,120 is four people and their appliances, and 6,300 is moisture the coil has to wring out of Clemson'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 28,800 BTU/hr before the moisture allowance.

Other house sizes in Clemson

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 6,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,600 BTU/hr.

Month by month in Clemson

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 1,000 hours a year at full output.

Clemson against nearby cities

Of 42 South Carolina cities here, Clemson has the 41st highest cooling load. The range runs from Gaffney at 32,300 BTU/hr to Columbia at 43,100.

Where Clemson's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Clemson Oconee County Airport, 4.1 miles from the center of Clemson at 889 ft above sea level. That is close enough that the station's summers are Clemson's summers.

No other city in this set uses Clemson Oconee County Airport, so this sizing is Clemson's alone.

The sun over Clemson in late July

At 34.68°N, the noon sun on 21 July stands 75.7° above the horizon over Clemson and the day runs 13 h 59 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.

18,610 people live in Clemson, the 28th largest of the 42 South Carolina cities sized on this site. Coordinates used: 34.6836, -82.8106.

Clemson AC sizing questions