What size AC for Pella, IA? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 26,400 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 59% 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 908 square feet in this climate. For a single room, size by the room: 13.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Des Moines 17 E (21.7 mi away). Jul is the hottest month, averaging a high of 83.5°F and a low of 63.8°F, with about 14 days a year at 90°F or more. That gives a design temperature of 88°F against 75°F inside.

What it costs to run

About 1,065 kWh a year at SEER2 14.3, or roughly $155 at Iowa's average residential rate of 14.55¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Pella

Of the 26,400 BTU/hr, 9,360 comes through walls, roof and windows on a 88°F afternoon (35%), 13,000 is sun on the house (49%), 2,120 is four people and their appliances, and 2,000 is moisture the coil has to wring out of Pella's summer air (8%).

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 24,480 BTU/hr before the moisture allowance.

Other house sizes in Pella

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,000 BTU/hr; a 350 sq ft living room needs about 4,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,900 BTU/hr.

Month by month in Pella

Jul alone uses 33% of the year's cooling energy. The unit runs the equivalent of 576 hours a year at full output.

Pella against nearby cities

Of 41 Iowa cities here, Pella has the 34th highest cooling load. The range runs from Dubuque at 24,900 BTU/hr to Council Bluffs at 34,300.

Where Pella's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Des Moines 17 E, 21.7 miles from the center of Pella at 921 ft above sea level. That is close enough that the station's summers are Pella's summers.

2 other cities use the same station and get the same climate inputs. The closest to Pella: Newton (21 mi away, 15.9 mi from the station), Altoona (34 mi away, 12 mi from the station). Pella is farther from the station than 2 of them.

The sun over Pella in late July

At 41.40°N, the noon sun on 21 July stands 69.0° above the horizon over Pella and the day runs 14 h 33 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.

10,965 people live in Pella, the 38th largest of the 41 Iowa cities sized on this site. Coordinates used: 41.4047, -92.9174.

Pella AC sizing questions