What size AC for Big Spring, TX? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 46,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, which falls short here. On a design day the unit runs flat out and the house still drifts above 75°F by late afternoon.

If a contractor quotes you more than 4 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 513 square feet in this climate. For a single room, size by the room: 23.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Big Spring (1.9 mi away). Jul is the hottest month, averaging a high of 95.8°F and a low of 72.1°F, with about 115 days a year at 90°F or more. That gives a design temperature of 104°F against 75°F inside.

What it costs to run

About 3,940 kWh a year at SEER2 14.3, or roughly $632 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Big Spring

Of the 46,800 BTU/hr, 20,880 comes through walls, roof and windows on a 104°F afternoon (45%), 13,000 is sun on the house (28%), 2,120 is four people and their appliances, and 10,800 is moisture the coil has to wring out of Big Spring'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 36,000 BTU/hr before the moisture allowance.

Other house sizes in Big Spring

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,500 BTU/hr; a 350 sq ft living room needs about 8,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 14,000 BTU/hr.

Month by month in Big Spring

Jul alone uses 23% of the year's cooling energy. The unit runs the equivalent of 1,204 hours a year at full output.

Big Spring against nearby cities

Of 252 Texas cities here, Big Spring has the 98th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Big Spring's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Big Spring, 1.9 miles from the center of Big Spring at 2,510 ft above sea level. That is close enough that the station's summers are Big Spring's summers.

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

The sun over Big Spring in late July

At 32.24°N, the noon sun on 21 July stands 78.2° above the horizon over Big Spring and the day runs 13 h 49 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.

22,541 people live in Big Spring, the 143rd largest of the 252 Texas cities sized on this site. Coordinates used: 32.2383, -101.4857.

Big Spring AC sizing questions