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

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

3.5 tons central AC or heat pump, about 39,500 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.3 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 607 square feet in this climate. For a single room, size by the room: 19.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Magnolia (2.8 mi away). Aug is the hottest month, averaging a high of 92.7°F and a low of 68.5°F, with about 76 days a year at 90°F or more. That gives a design temperature of 99°F against 75°F inside.

What it costs to run

About 2,961 kWh a year at SEER2 14.3, or roughly $407 at Arkansas's average residential rate of 13.74¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Magnolia

Of the 39,500 BTU/hr, 17,280 comes through walls, roof and windows on a 99°F afternoon (44%), 13,000 is sun on the house (33%), 2,120 is four people and their appliances, and 7,100 is moisture the coil has to wring out of Magnolia'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 32,400 BTU/hr before the moisture allowance.

Other house sizes in Magnolia

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,000 BTU/hr; a 350 sq ft living room needs about 6,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,900 BTU/hr.

Month by month in Magnolia

Jul alone uses 25% of the year's cooling energy. The unit runs the equivalent of 1,071 hours a year at full output.

Magnolia against nearby cities

Of 39 Arkansas cities here, Magnolia has the 16th highest cooling load. The range runs from Harrison at 33,100 BTU/hr to Fort Smith at 44,000.

Where Magnolia's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Magnolia, 2.8 miles from the center of Magnolia at 372 ft above sea level. That is close enough that the station's summers are Magnolia's summers.

No other city in this set uses Magnolia, so this sizing is Magnolia's alone.

The sun over Magnolia in late July

At 33.28°N, the noon sun on 21 July stands 77.1° above the horizon over Magnolia and the day runs 13 h 53 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.

10,759 people live in Magnolia, the 36th largest of the 39 Arkansas cities sized on this site. Coordinates used: 33.2767, -93.2262.

Magnolia AC sizing questions