What size AC for Alamogordo, NM? 3.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Alamogordo 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 Alamogordo (2.4 mi away). Jun is the hottest month, averaging a high of 94°F and a low of 68.1°F, with about 89 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 3,002 kWh a year at SEER2 14.3, or roughly $461 at New Mexico's average residential rate of 15.34¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Alamogordo

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 Alamogordo'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 Alamogordo

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 Alamogordo

Jul alone uses 25% of the year's cooling energy. The unit runs the equivalent of 1,040 hours a year at full output.

Alamogordo against nearby cities

Of 19 New Mexico cities here, Alamogordo has the 5th highest cooling load. The range runs from Las Vegas at 25,500 BTU/hr to Sunland Park at 44,800.

Where Alamogordo's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Alamogordo, 2.4 miles from the center of Alamogordo at 4,380 ft above sea level. That is close enough that the station's summers are Alamogordo's summers.

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

The sun over Alamogordo in late July

At 32.88°N, the noon sun on 21 July stands 77.5° above the horizon over Alamogordo and the day runs 13 h 51 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.

31,667 people live in Alamogordo, the 10th largest of the 19 New Mexico cities sized on this site. Coordinates used: 32.8836, -105.9636.

Alamogordo AC sizing questions