What size AC for Prineville, OR? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 29,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 44% 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 2.5 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 822 square feet in this climate. For a single room, size by the room: 14.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Redmond Airport (14.2 mi away). Jul is the hottest month, averaging a high of 87.5°F and a low of 48.5°F, with about 32 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 399 kWh a year at SEER2 14.3, or roughly $62 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Prineville

Of the 29,200 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (44%), 13,000 is sun on the house (45%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Prineville's summer air (4%).

Sun is the biggest share here, more than heat through the walls, so shading west windows and a light roof cut the size you need more than extra insulation would. Sensible heat totals 28,080 BTU/hr before the moisture allowance.

Other house sizes in Prineville

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,200 BTU/hr; a 350 sq ft living room needs about 5,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,800 BTU/hr.

Month by month in Prineville

Jul alone uses 43% of the year's cooling energy. The unit runs the equivalent of 195 hours a year at full output.

Prineville against nearby cities

Of 57 Oregon cities here, Prineville has the 10th highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where Prineville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Redmond Airport, 14.2 miles from the center of Prineville at 3,049 ft above sea level. That is close enough that the station's summers are Prineville's summers.

2 other cities use the same station and get the same climate inputs. The closest to Prineville: Redmond (16 mi away, 2.1 mi from the station), Bend (28 mi away, 16.1 mi from the station). Prineville is farther from the station than 1 of them.

The sun over Prineville in late July

At 44.30°N, the noon sun on 21 July stands 66.1° above the horizon over Prineville and the day runs 14 h 50 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. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

11,917 people live in Prineville, the 45th largest of the 57 Oregon cities sized on this site. Coordinates used: 44.2985, -120.8607.

Prineville AC sizing questions