What size AC for Cairo, GA? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 37,800 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.1 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 635 square feet in this climate. For a single room, size by the room: 18.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Cairo 1sw (1 mi away). Aug is the hottest month, averaging a high of 90.3°F and a low of 71.2°F, with about 78 days a year at 90°F or more. That gives a design temperature of 97°F against 75°F inside.

What it costs to run

About 3,430 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 Cairo

Of the 37,800 BTU/hr, 15,840 comes through walls, roof and windows on a 97°F afternoon (42%), 13,000 is sun on the house (34%), 2,120 is four people and their appliances, and 6,800 is moisture the coil has to wring out of Cairo'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 30,960 BTU/hr before the moisture allowance.

Other house sizes in Cairo

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,800 BTU/hr; a 350 sq ft living room needs about 6,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,300 BTU/hr.

Month by month in Cairo

Aug alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,299 hours a year at full output.

Cairo against nearby cities

Of 101 Georgia cities here, Cairo has the 37th highest cooling load. The range runs from Cumming at 33,100 BTU/hr to Albany at 44,000.

Where Cairo's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Cairo 1sw, 1 miles from the center of Cairo at 201 ft above sea level. That is close enough that the station's summers are Cairo's summers.

1 other city uses the same station and get the same climate inputs. The closest to Cairo: Thomasville (14 mi away, 14.3 mi from the station). Cairo sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Cairo in late July

At 30.88°N, the noon sun on 21 July stands 79.5° above the horizon over Cairo and the day runs 13 h 43 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.

10,057 people live in Cairo, the 101st largest of the 101 Georgia cities sized on this site. Coordinates used: 30.8792, -84.2055.

Cairo AC sizing questions