What size AC for Laurel, MS? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 40,400 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 594 square feet in this climate. For a single room, size by the room: 20.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Laurel (1.8 mi away). Jul is the hottest month, averaging a high of 93.2°F and a low of 70.3°F, with about 82 days a year at 90°F or more. That gives a design temperature of 100°F against 75°F inside.

What it costs to run

About 3,452 kWh a year at SEER2 14.3, or roughly $520 at Mississippi's average residential rate of 15.06¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Laurel

Of the 40,400 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (45%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 7,300 is moisture the coil has to wring out of Laurel'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 33,120 BTU/hr before the moisture allowance.

Other house sizes in Laurel

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 7,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,100 BTU/hr.

Month by month in Laurel

Jul alone uses 22% of the year's cooling energy. The unit runs the equivalent of 1,222 hours a year at full output.

Laurel against nearby cities

Of 41 Mississippi cities here, Laurel has the 21st highest cooling load. The range runs from Brookhaven at 36,900 BTU/hr to Columbus at 44,000.

Where Laurel's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Laurel, 1.8 miles from the center of Laurel at 225 ft above sea level. That is close enough that the station's summers are Laurel's summers.

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

The sun over Laurel in late July

At 31.69°N, the noon sun on 21 July stands 78.7° above the horizon over Laurel 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.

17,508 people live in Laurel, the 24th largest of the 41 Mississippi cities sized on this site. Coordinates used: 31.6912, -89.1483.

Laurel AC sizing questions