What size AC for Scottsboro, AL? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 35,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 20% 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 683 square feet in this climate. For a single room, size by the room: 17.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Scottsboro 2 Ne (4.4 mi away). Jul is the hottest month, averaging a high of 88.3°F and a low of 68°F, with about 46 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 2,244 kWh a year at SEER2 14.3, or roughly $370 at Alabama's average residential rate of 16.51¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Scottsboro

Of the 35,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (39%), 13,000 is sun on the house (37%), 2,120 is four people and their appliances, and 6,300 is moisture the coil has to wring out of Scottsboro'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 28,800 BTU/hr before the moisture allowance.

Other house sizes in Scottsboro

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,600 BTU/hr.

Month by month in Scottsboro

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 913 hours a year at full output.

Scottsboro against nearby cities

Of 66 Alabama cities here, Scottsboro has the 60th highest cooling load. The range runs from Boaz at 30,600 BTU/hr to Montgomery at 44,000.

Where Scottsboro's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Scottsboro 2 Ne, 4.4 miles from the center of Scottsboro at 636 ft above sea level. That is close enough that the station's summers are Scottsboro's summers.

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

The sun over Scottsboro in late July

At 34.64°N, the noon sun on 21 July stands 75.8° above the horizon over Scottsboro and the day runs 13 h 59 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.

15,957 people live in Scottsboro, the 46th largest of the 66 Alabama cities sized on this site. Coordinates used: 34.6446, -86.0482.

Scottsboro AC sizing questions