What size AC for Siloam Springs, AR? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 36,900 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.1 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 651 square feet in this climate. For a single room, size by the room: 18.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Fayetteville Springdale Nw Ar (14.2 mi away). Jul is the hottest month, averaging a high of 90.3°F and a low of 68.5°F, with about 45 days a year at 90°F or more. That gives a design temperature of 96°F against 75°F inside.

What it costs to run

About 2,302 kWh a year at SEER2 14.3, or roughly $316 at Arkansas's average residential rate of 13.74¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Siloam Springs

Of the 36,900 BTU/hr, 15,120 comes through walls, roof and windows on a 96°F afternoon (41%), 13,000 is sun on the house (35%), 2,120 is four people and their appliances, and 6,700 is moisture the coil has to wring out of Siloam Springs'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 30,240 BTU/hr before the moisture allowance.

Other house sizes in Siloam Springs

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,800 BTU/hr; a 350 sq ft living room needs about 6,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,000 BTU/hr.

Month by month in Siloam Springs

Jul alone uses 29% of the year's cooling energy. The unit runs the equivalent of 892 hours a year at full output.

Siloam Springs against nearby cities

Of 39 Arkansas cities here, Siloam Springs has the 32nd highest cooling load. The range runs from Harrison at 33,100 BTU/hr to Fort Smith at 44,000.

Where Siloam Springs's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Fayetteville Springdale Nw Ar, 14.2 miles from the center of Siloam Springs at 1,278 ft above sea level. That is close enough that the station's summers are Siloam Springs's summers.

7 other cities use the same station and get the same climate inputs. The closest to Siloam Springs: Centerton (17 mi away, 4.6 mi from the station), Bentonville (20 mi away, 6.2 mi from the station), Springdale (21 mi away, 11 mi from the station), Lowell (22 mi away, 9.1 mi from the station), Rogers (23 mi away, 9.1 mi from the station). Siloam Springs is farther from the station than 6 of them.

The sun over Siloam Springs in late July

At 36.19°N, the noon sun on 21 July stands 74.2° above the horizon over Siloam Springs and the day runs 14 h 06 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.

20,075 people live in Siloam Springs, the 25th largest of the 39 Arkansas cities sized on this site. Coordinates used: 36.1854, -94.5300.

Siloam Springs AC sizing questions