What size AC for Prescott, AZ? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 32,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 29% more than this climate needs. An oversized unit cools the air fast, shuts off before it pulls moisture out, and leaves the house cold and clammy.

If a contractor quotes you more than 3 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 735 square feet in this climate. For a single room, size by the room: 16.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Prescott Love Field (4.2 mi away). Jul is the hottest month, averaging a high of 90.3°F and a low of 62.7°F, with about 50 days a year at 90°F or more. That gives a design temperature of 96°F against 75°F inside.

What it costs to run

About 1,394 kWh a year at SEER2 14.3, or roughly $214 at Arizona's average residential rate of 15.36¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Prescott

Of the 32,700 BTU/hr, 15,120 comes through walls, roof and windows on a 96°F afternoon (46%), 13,000 is sun on the house (40%), 2,120 is four people and their appliances, and 2,400 is moisture the coil has to wring out of Prescott's summer air (7%).

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 30,240 BTU/hr before the moisture allowance.

Other house sizes in Prescott

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,800 BTU/hr.

Month by month in Prescott

Jul alone uses 33% of the year's cooling energy. The unit runs the equivalent of 610 hours a year at full output.

Prescott against nearby cities

Of 44 Arizona cities here, Prescott has the 41st highest cooling load. The range runs from Flagstaff at 24,000 BTU/hr to Bullhead City at 60,800.

Where Prescott's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Prescott Love Field, 4.2 miles from the center of Prescott at 5,013 ft above sea level. That is close enough that the station's summers are Prescott's summers.

2 other cities use the same station and get the same climate inputs. The closest to Prescott: Prescott Valley (7 mi away, 6.9 mi from the station), Chino Valley (10 mi away, 6.3 mi from the station). Prescott sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Prescott in late July

At 34.59°N, the noon sun on 21 July stands 75.8° above the horizon over Prescott and the day runs 13 h 59 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.

48,224 people live in Prescott, the 23rd largest of the 44 Arizona cities sized on this site. Coordinates used: 34.5922, -112.4467.

Prescott AC sizing questions