What size AC for Garden City, GA? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 42,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 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 570 square feet in this climate. For a single room, size by the room: 21.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Savannah International Airport (3.4 mi away). Jul is the hottest month, averaging a high of 92.3°F and a low of 73.7°F, with about 81 days a year at 90°F or more. That gives a design temperature of 99°F against 75°F inside.

What it costs to run

About 4,078 kWh a year at SEER2 14.3, or roughly $631 at Georgia's average residential rate of 15.48¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Garden City

Of the 42,100 BTU/hr, 17,280 comes through walls, roof and windows on a 99°F afternoon (41%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 9,700 is moisture the coil has to wring out of Garden City'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 32,400 BTU/hr before the moisture allowance.

Other house sizes in Garden City

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 7,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,700 BTU/hr.

Month by month in Garden City

Jul alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,385 hours a year at full output.

Garden City against nearby cities

Of 101 Georgia cities here, Garden City has the 12th highest cooling load. The range runs from Cumming at 33,100 BTU/hr to Albany at 44,000.

Where Garden City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Savannah International Airport, 3.4 miles from the center of Garden City at 29 ft above sea level. That is close enough that the station's summers are Garden City's summers.

7 other cities use the same station and get the same climate inputs. The closest to Garden City: Pooler (5 mi away, 3.6 mi from the station), Savannah (5 mi away, 8.2 mi from the station), Port Wentworth (7 mi away, 4.2 mi from the station), Rincon (15 mi away, 11.4 mi from the station), Richmond Hill (15 mi away, 17.2 mi from the station). Garden City sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Garden City in late July

At 32.09°N, the noon sun on 21 July stands 78.3° above the horizon over Garden City and the day runs 13 h 48 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.

10,536 people live in Garden City, the 96th largest of the 101 Georgia cities sized on this site. Coordinates used: 32.0872, -81.1766.

Garden City AC sizing questions