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

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

4 tons central AC or heat pump, about 42,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 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 570 square feet in this climate. For a single room, size by the room: 21.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Grand Coteau (7.7 mi away). Aug is the hottest month, averaging a high of 92°F and a low of 72.3°F, with about 93 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 4,238 kWh a year at SEER2 14.3, or roughly $562 at Louisiana's average residential rate of 13.27¢ per kWh. Cooling runs 8 months of the year here.

What drives the load in Opelousas

Of the 42,100 BTU/hr, 17,280 comes through walls, roof and windows on a 99°F afternoon (41%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 9,700 is moisture the coil has to wring out of Opelousas'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 32,400 BTU/hr before the moisture allowance.

Other house sizes in Opelousas

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,700 BTU/hr.

Month by month in Opelousas

Aug alone uses 20% of the year's cooling energy. The unit runs the equivalent of 1,439 hours a year at full output.

Opelousas against nearby cities

Of 35 Louisiana cities here, Opelousas has the 16th highest cooling load. The range runs from Covington at 37,800 BTU/hr to Natchitoches at 45,900.

Where Opelousas's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Grand Coteau, 7.7 miles from the center of Opelousas at 55 ft above sea level. That is close enough that the station's summers are Opelousas's summers.

No other city in this set uses Grand Coteau, so this sizing is Opelousas's alone.

The sun over Opelousas in late July

At 30.52°N, the noon sun on 21 July stands 79.9° above the horizon over Opelousas and the day runs 13 h 41 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.

15,176 people live in Opelousas, the 23rd largest of the 35 Louisiana cities sized on this site. Coordinates used: 30.5249, -92.0817.

Opelousas AC sizing questions