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

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

4 tons central AC or heat pump, about 45,500 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.8 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 527 square feet in this climate. For a single room, size by the room: 22.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Tuzigoot (2.8 mi away). Jul is the hottest month, averaging a high of 101.1°F and a low of 66.8°F, with about 128 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 2,968 kWh a year at SEER2 14.3, or roughly $456 at Arizona's average residential rate of 15.36¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Cottonwood

Of the 45,500 BTU/hr, 24,480 comes through walls, roof and windows on a 109°F afternoon (54%), 13,000 is sun on the house (29%), 2,120 is four people and their appliances, and 5,900 is moisture the coil has to wring out of Cottonwood's summer air (13%).

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 Cottonwood

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,400 BTU/hr; a 350 sq ft living room needs about 8,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 13,700 BTU/hr.

Month by month in Cottonwood

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 932 hours a year at full output.

Cottonwood against nearby cities

Of 44 Arizona cities here, Cottonwood has the 33rd highest cooling load. The range runs from Flagstaff at 24,000 BTU/hr to Bullhead City at 60,800.

Where Cottonwood's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Tuzigoot, 2.8 miles from the center of Cottonwood at 3,470 ft above sea level. That is close enough that the station's summers are Cottonwood's summers.

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

The sun over Cottonwood in late July

At 34.75°N, the noon sun on 21 July stands 75.6° above the horizon over Cottonwood and the day runs 13 h 60 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.

12,939 people live in Cottonwood, the 40th largest of the 44 Arizona cities sized on this site. Coordinates used: 34.7508, -111.9840.

Cottonwood AC sizing questions