What size AC for Hobbs, NM? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 42,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 tons. This is one of the climates the chart was written for.

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 569 square feet in this climate. For a single room, size by the room: 21.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Hobbs (1.7 mi away). Jul is the hottest month, averaging a high of 94.1°F and a low of 68.7°F, with about 104 days a year at 90°F or more. That gives a design temperature of 102°F against 75°F inside.

What it costs to run

About 2,921 kWh a year at SEER2 14.3, or roughly $448 at New Mexico's average residential rate of 15.34¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Hobbs

Of the 42,200 BTU/hr, 19,440 comes through walls, roof and windows on a 102°F afternoon (46%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 7,600 is moisture the coil has to wring out of Hobbs'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 34,560 BTU/hr before the moisture allowance.

Other house sizes in Hobbs

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,700 BTU/hr.

Month by month in Hobbs

Jul alone uses 26% of the year's cooling energy. The unit runs the equivalent of 991 hours a year at full output.

Hobbs against nearby cities

Of 19 New Mexico cities here, Hobbs has the 3rd highest cooling load. The range runs from Las Vegas at 25,500 BTU/hr to Sunland Park at 44,800.

Where Hobbs's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Hobbs, 1.7 miles from the center of Hobbs at 3,660 ft above sea level. That is close enough that the station's summers are Hobbs's summers.

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

The sun over Hobbs in late July

At 32.73°N, the noon sun on 21 July stands 77.7° above the horizon over Hobbs 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.

41,061 people live in Hobbs, the 7th largest of the 19 New Mexico cities sized on this site. Coordinates used: 32.7291, -103.1606.

Hobbs AC sizing questions