What size AC for Shelbyville, TN? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 36,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 17% 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 666 square feet in this climate. For a single room, size by the room: 18 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Shelbyville Water Dept (1.5 mi away). Jul is the hottest month, averaging a high of 89.4°F and a low of 68.3°F, with about 49 days a year at 90°F or more. That gives a design temperature of 95°F against 75°F inside.

What it costs to run

About 2,362 kWh a year at SEER2 14.3, or roughly $326 at Tennessee's average residential rate of 13.8¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Shelbyville

Of the 36,000 BTU/hr, 14,400 comes through walls, roof and windows on a 95°F afternoon (40%), 13,000 is sun on the house (36%), 2,120 is four people and their appliances, and 6,500 is moisture the coil has to wring out of Shelbyville's summer air (18%).

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 29,520 BTU/hr before the moisture allowance.

Other house sizes in Shelbyville

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,700 BTU/hr; a 350 sq ft living room needs about 6,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,800 BTU/hr.

Month by month in Shelbyville

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 938 hours a year at full output.

Shelbyville against nearby cities

Of 65 Tennessee cities here, Shelbyville has the 30th highest cooling load. The range runs from Crossville at 27,300 BTU/hr to Memphis at 41,200.

Where Shelbyville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Shelbyville Water Dept, 1.5 miles from the center of Shelbyville at 760 ft above sea level. That is close enough that the station's summers are Shelbyville's summers.

No other city in this set uses Shelbyville Water Dept, so this sizing is Shelbyville's alone.

The sun over Shelbyville in late July

At 35.50°N, the noon sun on 21 July stands 74.9° above the horizon over Shelbyville and the day runs 14 h 03 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.

25,792 people live in Shelbyville, the 29th largest of the 65 Tennessee cities sized on this site. Coordinates used: 35.5013, -86.4529.

Shelbyville AC sizing questions