What size AC for Fort Smith, AR? 4 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Fort Smith 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 Fort Smith Regional Airport (1.1 mi away). Jul is the hottest month, averaging a high of 94.1°F and a low of 72.1°F, with about 78 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 3,420 kWh a year at SEER2 14.3, or roughly $470 at Arkansas's average residential rate of 13.74¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Fort Smith

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 Fort Smith'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 Fort Smith

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 Fort Smith

Jul alone uses 26% of the year's cooling energy. The unit runs the equivalent of 1,112 hours a year at full output.

Fort Smith against nearby cities

Of 39 Arkansas cities here, Fort Smith has the highest cooling load. The range runs from Harrison at 33,100 BTU/hr to Fort Smith at 44,000.

Where Fort Smith's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Fort Smith Regional Airport, 1.1 miles from the center of Fort Smith at 448 ft above sea level. That is close enough that the station's summers are Fort Smith's summers.

1 other city uses the same station and get the same climate inputs. The closest to Fort Smith: Van Buren (7 mi away, 8.2 mi from the station). Fort Smith sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Fort Smith in late July

At 35.35°N, the noon sun on 21 July stands 75.1° above the horizon over Fort Smith and the day runs 14 h 02 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.

90,507 people live in Fort Smith, the 3rd largest of the 39 Arkansas cities sized on this site. Coordinates used: 35.3493, -94.3709.

Fort Smith AC sizing questions