What size AC for Macon-Bibb County, GA? 3.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Macon-Bibb County 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 Macon Middle Ga Regional Airport (8.6 mi away). Jul is the hottest month, averaging a high of 93.5°F and a low of 71.5°F, with about 85 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 3,429 kWh a year at SEER2 14.3, or roughly $531 at Georgia's average residential rate of 15.48¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Macon-Bibb County

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 Macon-Bibb County'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 Macon-Bibb County

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 Macon-Bibb County

Jul alone uses 23% of the year's cooling energy. The unit runs the equivalent of 1,214 hours a year at full output.

Macon-Bibb County against nearby cities

Of 101 Georgia cities here, Macon-Bibb County has the 15th highest cooling load. The range runs from Cumming at 33,100 BTU/hr to Albany at 44,000.

Where Macon-Bibb County's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Macon Middle Ga Regional Airport, 8.6 miles from the center of Macon-Bibb County at 343 ft above sea level. That is close enough that the station's summers are Macon-Bibb County's summers.

2 other cities use the same station and get the same climate inputs. The closest to Macon-Bibb County: Warner Robins (15 mi away, 6.3 mi from the station), Perry (23 mi away, 15.5 mi from the station). Macon-Bibb County is farther from the station than 1 of them.

The sun over Macon-Bibb County in late July

At 32.81°N, the noon sun on 21 July stands 77.6° above the horizon over Macon-Bibb County and the day runs 13 h 51 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.

157,056 people live in Macon-Bibb County, the 4th largest of the 101 Georgia cities sized on this site. Coordinates used: 32.8090, -83.6941.

Macon-Bibb County AC sizing questions