What size AC for Atchison, KS? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 34,300 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 23% 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 701 square feet in this climate. For a single room, size by the room: 17.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Atchison (1.6 mi away). Jul is the hottest month, averaging a high of 87.6°F and a low of 69.3°F, with about 38 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 2,005 kWh a year at SEER2 14.3, or roughly $306 at Kansas's average residential rate of 15.26¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Atchison

Of the 34,300 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (38%), 13,000 is sun on the house (38%), 2,120 is four people and their appliances, and 6,200 is moisture the coil has to wring out of Atchison's summer air (18%).

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 Atchison

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,300 BTU/hr.

Month by month in Atchison

Jul alone uses 31% of the year's cooling energy. The unit runs the equivalent of 837 hours a year at full output.

Atchison against nearby cities

Of 38 Kansas cities here, Atchison has the 36th highest cooling load. The range runs from Pittsburg at 33,100 BTU/hr to Wichita at 39,500.

Where Atchison's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Atchison, 1.6 miles from the center of Atchison at 945 ft above sea level. That is close enough that the station's summers are Atchison's summers.

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

The sun over Atchison in late July

At 39.56°N, the noon sun on 21 July stands 70.8° above the horizon over Atchison and the day runs 14 h 23 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.

10,813 people live in Atchison, the 35th largest of the 38 Kansas cities sized on this site. Coordinates used: 39.5626, -95.1366.

Atchison AC sizing questions