What size AC for Natchitoches, LA? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 45,900 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.8 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 523 square feet in this climate. For a single room, size by the room: 22.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Natchitoches (2.6 mi away). Aug is the hottest month, averaging a high of 95.7°F and a low of 74.9°F, with about 98 days a year at 90°F or more. That gives a design temperature of 103°F against 75°F inside.

What it costs to run

About 4,731 kWh a year at SEER2 14.3, or roughly $628 at Louisiana's average residential rate of 13.27¢ per kWh. Cooling runs 8 months of the year here.

What drives the load in Natchitoches

Of the 45,900 BTU/hr, 20,160 comes through walls, roof and windows on a 103°F afternoon (44%), 13,000 is sun on the house (28%), 2,120 is four people and their appliances, and 10,600 is moisture the coil has to wring out of Natchitoches'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 35,280 BTU/hr before the moisture allowance.

Other house sizes in Natchitoches

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,400 BTU/hr; a 350 sq ft living room needs about 8,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 13,700 BTU/hr.

Month by month in Natchitoches

Jul alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,475 hours a year at full output.

Natchitoches against nearby cities

Of 35 Louisiana cities here, Natchitoches has the highest cooling load. The range runs from Covington at 37,800 BTU/hr to Natchitoches at 45,900.

Where Natchitoches's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Natchitoches, 2.6 miles from the center of Natchitoches at 130 ft above sea level. That is close enough that the station's summers are Natchitoches's summers.

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

The sun over Natchitoches in late July

At 31.73°N, the noon sun on 21 July stands 78.7° above the horizon over Natchitoches and the day runs 13 h 46 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.

17,165 people live in Natchitoches, the 20th largest of the 35 Louisiana cities sized on this site. Coordinates used: 31.7348, -93.1009.

Natchitoches AC sizing questions