What size AC for Florence, AZ? 5 tons for 2,000 sq ft

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

5 tons central AC or heat pump, about 55,200 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 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 435 square feet in this climate. For a single room, size by the room: 27.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Florence (2.7 mi away). Jul is the hottest month, averaging a high of 104.9°F and a low of 78.3°F, with about 169 days a year at 90°F or more. That gives a design temperature of 113°F against 75°F inside.

What it costs to run

About 6,090 kWh a year at SEER2 14.3, or roughly $935 at Arizona's average residential rate of 15.36¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Florence

Of the 55,200 BTU/hr, 27,360 comes through walls, roof and windows on a 113°F afternoon (50%), 13,000 is sun on the house (24%), 2,120 is four people and their appliances, and 12,700 is moisture the coil has to wring out of Florence'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 42,480 BTU/hr before the moisture allowance.

Other house sizes in Florence

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 4,100 BTU/hr; a 350 sq ft living room needs about 9,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 16,600 BTU/hr.

Month by month in Florence

Jul alone uses 21% of the year's cooling energy. The unit runs the equivalent of 1,577 hours a year at full output.

Florence against nearby cities

Of 44 Arizona cities here, Florence has the 19th highest cooling load. The range runs from Flagstaff at 24,000 BTU/hr to Bullhead City at 60,800.

Where Florence's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Florence, 2.7 miles from the center of Florence at 1,400 ft above sea level. That is close enough that the station's summers are Florence's summers.

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

The sun over Florence in late July

At 33.07°N, the noon sun on 21 July stands 77.3° above the horizon over Florence and the day runs 13 h 52 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.

24,891 people live in Florence, the 31st largest of the 44 Arizona cities sized on this site. Coordinates used: 33.0694, -111.4140.

Florence AC sizing questions