What size AC for Marshall, TX? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 41,300 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 581 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 Marshall (3.7 mi away). Aug is the hottest month, averaging a high of 94.2°F and a low of 70.3°F, with about 83 days a year at 90°F or more. That gives a design temperature of 101°F against 75°F inside.

What it costs to run

About 3,363 kWh a year at SEER2 14.3, or roughly $539 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Marshall

Of the 41,300 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (45%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 7,400 is moisture the coil has to wring out of Marshall'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 33,840 BTU/hr before the moisture allowance.

Other house sizes in Marshall

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 Marshall

Jul alone uses 24% of the year's cooling energy. The unit runs the equivalent of 1,165 hours a year at full output.

Marshall against nearby cities

Of 252 Texas cities here, Marshall has the 235th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Marshall's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Marshall, 3.7 miles from the center of Marshall at 302 ft above sea level. That is close enough that the station's summers are Marshall's summers.

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

The sun over Marshall in late July

At 32.54°N, the noon sun on 21 July stands 77.9° above the horizon over Marshall and the day runs 13 h 50 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.

24,263 people live in Marshall, the 138th largest of the 252 Texas cities sized on this site. Coordinates used: 32.5392, -94.3532.

Marshall AC sizing questions