What size AC for Tucson, AZ? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 48,300 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 497 square feet in this climate. For a single room, size by the room: 24.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Tucson International Airport (5.2 mi away). Jun is the hottest month, averaging a high of 101.2°F and a low of 71.1°F, with about 158 days a year at 90°F or more. That gives a design temperature of 109°F against 75°F inside.

What it costs to run

About 5,047 kWh a year at SEER2 14.3, or roughly $775 at Arizona's average residential rate of 15.36¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Tucson

Of the 48,300 BTU/hr, 24,480 comes through walls, roof and windows on a 109°F afternoon (51%), 13,000 is sun on the house (27%), 2,120 is four people and their appliances, and 8,700 is moisture the coil has to wring out of Tucson'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 39,600 BTU/hr before the moisture allowance.

Other house sizes in Tucson

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

Month by month in Tucson

Jul alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,494 hours a year at full output.

Tucson against nearby cities

Of 44 Arizona cities here, Tucson has the 28th highest cooling load. The range runs from Flagstaff at 24,000 BTU/hr to Bullhead City at 60,800.

Where Tucson's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Tucson International Airport, 5.2 miles from the center of Tucson at 2,551 ft above sea level. That is close enough that the station's summers are Tucson's summers.

1 other city uses the same station and get the same climate inputs. The closest to Tucson: Sahuarita (16 mi away, 13.8 mi from the station). Tucson sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Tucson in late July

At 32.15°N, the noon sun on 21 July stands 78.2° above the horizon over Tucson and the day runs 13 h 48 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.

554,013 people live in Tucson, the 2nd largest of the 44 Arizona cities sized on this site. Coordinates used: 32.1530, -110.8708.

Tucson AC sizing questions