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

What size AC a 2,000 sq ft house in Lufkin 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 Lufkin Angelina County Airport (6.2 mi away). Aug is the hottest month, averaging a high of 93.7°F and a low of 71.1°F, with about 104 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 3,721 kWh a year at SEER2 14.3, or roughly $596 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Lufkin

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 Lufkin'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 Lufkin

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 Lufkin

Jul alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,289 hours a year at full output.

Lufkin against nearby cities

Of 252 Texas cities here, Lufkin has the 234th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Lufkin's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lufkin Angelina County Airport, 6.2 miles from the center of Lufkin at 286 ft above sea level. That is close enough that the station's summers are Lufkin's summers.

No other city in this set uses Lufkin Angelina County Airport, so this sizing is Lufkin's alone.

The sun over Lufkin in late July

At 31.32°N, the noon sun on 21 July stands 79.1° above the horizon over Lufkin and the day runs 13 h 45 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.

34,399 people live in Lufkin, the 109th largest of the 252 Texas cities sized on this site. Coordinates used: 31.3229, -94.7290.

Lufkin AC sizing questions