What size AC for Prattville, AL? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 44,000 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.7 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 546 square feet in this climate. For a single room, size by the room: 22 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Montgomery Airport (10.6 mi away). Jul is the hottest month, averaging a high of 93.7°F and a low of 72.1°F, with about 93 days a year at 90°F or more. That gives a design temperature of 101°F against 75°F inside.

What it costs to run

About 3,990 kWh a year at SEER2 14.3, or roughly $659 at Alabama's average residential rate of 16.51¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Prattville

Of the 44,000 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (43%), 13,000 is sun on the house (30%), 2,120 is four people and their appliances, and 10,200 is moisture the coil has to wring out of Prattville'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 33,840 BTU/hr before the moisture allowance.

Other house sizes in Prattville

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,300 BTU/hr; a 350 sq ft living room needs about 7,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 13,200 BTU/hr.

Month by month in Prattville

Jul alone uses 22% of the year's cooling energy. The unit runs the equivalent of 1,297 hours a year at full output.

Prattville against nearby cities

Of 66 Alabama cities here, Prattville has the 2nd highest cooling load. The range runs from Boaz at 30,600 BTU/hr to Montgomery at 44,000.

Where Prattville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Montgomery Airport, 10.6 miles from the center of Prattville at 217 ft above sea level. That is close enough that the station's summers are Prattville's summers.

3 other cities use the same station and get the same climate inputs. The closest to Prattville: Millbrook (6 mi away, 14.1 mi from the station), Montgomery (13 mi away, 8.9 mi from the station), Pike Road (23 mi away, 17 mi from the station). Prattville is farther from the station than 1 of them.

The sun over Prattville in late July

At 32.45°N, the noon sun on 21 July stands 78.0° above the horizon over Prattville and the day runs 13 h 49 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.

40,139 people live in Prattville, the 12th largest of the 66 Alabama cities sized on this site. Coordinates used: 32.4490, -86.4494.

Prattville AC sizing questions