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

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

3 tons central AC or heat pump, about 31,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 33% 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 763 square feet in this climate. For a single room, size by the room: 15.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Valley Head 1 Ssw (8.5 mi away). Jul is the hottest month, averaging a high of 86.9°F and a low of 66.3°F, with about 26 days a year at 90°F or more. That gives a design temperature of 92°F against 75°F inside.

What it costs to run

About 1,807 kWh a year at SEER2 14.3, or roughly $298 at Alabama's average residential rate of 16.51¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Fort Payne

Of the 31,500 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (39%), 13,000 is sun on the house (41%), 2,120 is four people and their appliances, and 4,100 is moisture the coil has to wring out of Fort Payne's summer air (13%).

Sun is the biggest share here, more than heat through the walls, so shading west windows and a light roof cut the size you need more than extra insulation would. Sensible heat totals 27,360 BTU/hr before the moisture allowance.

Other house sizes in Fort Payne

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,400 BTU/hr.

Month by month in Fort Payne

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 821 hours a year at full output.

Fort Payne against nearby cities

Of 66 Alabama cities here, Fort Payne has the 64th highest cooling load. The range runs from Boaz at 30,600 BTU/hr to Montgomery at 44,000.

Where Fort Payne's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Valley Head 1 Ssw, 8.5 miles from the center of Fort Payne at 1,020 ft above sea level. That is close enough that the station's summers are Fort Payne's summers.

No other city in this set uses Valley Head 1 Ssw, so this sizing is Fort Payne's alone.

The sun over Fort Payne in late July

At 34.46°N, the noon sun on 21 July stands 75.9° above the horizon over Fort Payne and the day runs 13 h 58 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.

15,017 people live in Fort Payne, the 48th largest of the 66 Alabama cities sized on this site. Coordinates used: 34.4573, -85.6894.

Fort Payne AC sizing questions