What size AC for Mitchell, SD? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 29,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 42% 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 812 square feet in this climate. For a single room, size by the room: 14.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Mitchell Airport (3.3 mi away). Jul is the hottest month, averaging a high of 86.7°F and a low of 63.9°F, with about 28 days a year at 90°F or more. That gives a design temperature of 92°F against 75°F inside.

What it costs to run

About 1,148 kWh a year at SEER2 14.3, or roughly $167 at South Dakota's average residential rate of 14.58¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Mitchell

Of the 29,500 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (41%), 13,000 is sun on the house (44%), 2,120 is four people and their appliances, and 2,200 is moisture the coil has to wring out of Mitchell's summer air (7%).

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 27,360 BTU/hr before the moisture allowance.

Other house sizes in Mitchell

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 5,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,900 BTU/hr.

Month by month in Mitchell

Jul alone uses 37% of the year's cooling energy. The unit runs the equivalent of 556 hours a year at full output.

Mitchell against nearby cities

Of 14 South Dakota cities here, Mitchell has the 3rd highest cooling load. The range runs from Watertown at 24,900 BTU/hr to Pierre at 31,100.

Where Mitchell's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Mitchell Airport, 3.3 miles from the center of Mitchell at 1,301 ft above sea level. That is close enough that the station's summers are Mitchell's summers.

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

The sun over Mitchell in late July

At 43.73°N, the noon sun on 21 July stands 66.7° above the horizon over Mitchell and the day runs 14 h 47 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.

15,621 people live in Mitchell, the 7th largest of the 14 South Dakota cities sized on this site. Coordinates used: 43.7271, -98.0422.

Mitchell AC sizing questions