What size AC for Houma, LA? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 41,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.4 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 583 square feet in this climate. For a single room, size by the room: 20.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Houma (7.8 mi away). Aug is the hottest month, averaging a high of 91.4°F and a low of 74.5°F, with about 76 days a year at 90°F or more. That gives a design temperature of 98°F against 75°F inside.

What it costs to run

About 4,664 kWh a year at SEER2 14.3, or roughly $619 at Louisiana's average residential rate of 13.27¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Houma

Of the 41,200 BTU/hr, 16,560 comes through walls, roof and windows on a 98°F afternoon (40%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 9,500 is moisture the coil has to wring out of Houma'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 31,680 BTU/hr before the moisture allowance.

Other house sizes in Houma

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,100 BTU/hr; a 350 sq ft living room needs about 7,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,400 BTU/hr.

Month by month in Houma

Aug alone uses 19% of the year's cooling energy. The unit runs the equivalent of 1,620 hours a year at full output.

Houma against nearby cities

Of 35 Louisiana cities here, Houma has the 28th highest cooling load. The range runs from Covington at 37,800 BTU/hr to Natchitoches at 45,900.

Where Houma's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Houma, 7.8 miles from the center of Houma at 8 ft above sea level. That is close enough that the station's summers are Houma's summers.

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

The sun over Houma in late July

At 29.58°N, the noon sun on 21 July stands 80.8° above the horizon over Houma and the day runs 13 h 37 min from sunrise to sunset. With the sun that close to overhead, the roof takes most of the heat at midday and the west wall takes the rest after 3 pm. Shorter days give the house a longer night to shed the day's heat.

31,671 people live in Houma, the 10th largest of the 35 Louisiana cities sized on this site. Coordinates used: 29.5787, -90.7080.

Houma AC sizing questions