What size AC for Cumming, GA? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 33,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 27% 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 725 square feet in this climate. For a single room, size by the room: 16.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Cumming 2n (1.6 mi away). Jul is the hottest month, averaging a high of 88.8°F and a low of 67.4°F, with about 32 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 2,057 kWh a year at SEER2 14.3, or roughly $318 at Georgia's average residential rate of 15.48¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Cumming

Of the 33,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (41%), 13,000 is sun on the house (39%), 2,120 is four people and their appliances, and 4,300 is moisture the coil has to wring out of Cumming's summer air (13%).

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 Cumming

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,500 BTU/hr; a 350 sq ft living room needs about 5,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,000 BTU/hr.

Month by month in Cumming

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 888 hours a year at full output.

Cumming against nearby cities

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

Where Cumming's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Cumming 2n, 1.6 miles from the center of Cumming at 1,140 ft above sea level. That is close enough that the station's summers are Cumming's summers.

No other city in this set uses Cumming 2n, so this sizing is Cumming's alone.

The sun over Cumming in late July

At 34.21°N, the noon sun on 21 July stands 76.2° above the horizon over Cumming and the day runs 13 h 57 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.

10,175 people live in Cumming, the 99th largest of the 101 Georgia cities sized on this site. Coordinates used: 34.2061, -84.1338.

Cumming AC sizing questions