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

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

3.5 tons central AC or heat pump, about 39,300 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 611 square feet in this climate. For a single room, size by the room: 19.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Morgan City (2.1 mi away). Jul is the hottest month, averaging a high of 90.5°F and a low of 76.3°F, with about 53 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 4,813 kWh a year at SEER2 14.3, or roughly $639 at Louisiana's average residential rate of 13.27¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Morgan City

Of the 39,300 BTU/hr, 15,120 comes through walls, roof and windows on a 96°F afternoon (38%), 13,000 is sun on the house (33%), 2,120 is four people and their appliances, and 9,100 is moisture the coil has to wring out of Morgan City'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 30,240 BTU/hr before the moisture allowance.

Other house sizes in Morgan City

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 11,800 BTU/hr.

Month by month in Morgan City

Jul alone uses 19% of the year's cooling energy. The unit runs the equivalent of 1,751 hours a year at full output.

Morgan City against nearby cities

Of 35 Louisiana cities here, Morgan City has the 34th highest cooling load. The range runs from Covington at 37,800 BTU/hr to Natchitoches at 45,900.

Where Morgan City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Morgan City, 2.1 miles from the center of Morgan City at 5 ft above sea level. That is close enough that the station's summers are Morgan City's summers.

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

The sun over Morgan City in late July

At 29.71°N, the noon sun on 21 July stands 80.7° above the horizon over Morgan City and the day runs 13 h 38 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.

10,813 people live in Morgan City, the 34th largest of the 35 Louisiana cities sized on this site. Coordinates used: 29.7103, -91.1915.

Morgan City AC sizing questions