What size AC for Forest Acres, SC? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 43,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.6 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 4 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 557 square feet in this climate. For a single room, size by the room: 21.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Columbia Owens Dwtn Airport (4.4 mi away). Jul is the hottest month, averaging a high of 93.2°F and a low of 73.3°F, with about 83 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 3,798 kWh a year at SEER2 14.3, or roughly $604 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 Forest Acres

Of the 43,100 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (42%), 13,000 is sun on the house (30%), 2,120 is four people and their appliances, and 9,900 is moisture the coil has to wring out of Forest Acres'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 33,120 BTU/hr before the moisture allowance.

Other house sizes in Forest Acres

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,900 BTU/hr.

Month by month in Forest Acres

Jul alone uses 23% of the year's cooling energy. The unit runs the equivalent of 1,261 hours a year at full output.

Forest Acres against nearby cities

Of 42 South Carolina cities here, Forest Acres has the 5th highest cooling load. The range runs from Gaffney at 32,300 BTU/hr to Columbia at 43,100.

Where Forest Acres's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Columbia Owens Dwtn Airport, 4.4 miles from the center of Forest Acres at 180 ft above sea level. That is close enough that the station's summers are Forest Acres's summers.

2 other cities use the same station and get the same climate inputs. The closest to Forest Acres: Columbia (4 mi away, 6.9 mi from the station), Cayce (7 mi away, 3 mi from the station). Forest Acres is farther from the station than 1 of them.

The sun over Forest Acres in late July

At 34.03°N, the noon sun on 21 July stands 76.4° above the horizon over Forest Acres and the day runs 13 h 56 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.

10,438 people live in Forest Acres, the 42nd largest of the 42 South Carolina cities sized on this site. Coordinates used: 34.0331, -80.9732.

Forest Acres AC sizing questions