What size AC for Lexington-Fayette urban county, KY? 3 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Lexington-Fayette urban county needs

3 tons central AC or heat pump, about 31,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 33% 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 763 square feet in this climate. For a single room, size by the room: 15.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Lexington Bluegrass Airport (8.3 mi away). Jul is the hottest month, averaging a high of 86.9°F and a low of 66.5°F, with about 25 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 1,791 kWh a year at SEER2 14.3, or roughly $254 at Kentucky's average residential rate of 14.2¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Lexington-Fayette urban county

Of the 31,500 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (39%), 13,000 is sun on the house (41%), 2,120 is four people and their appliances, and 4,100 is moisture the coil has to wring out of Lexington-Fayette urban county's summer air (13%).

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 Lexington-Fayette urban county

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,400 BTU/hr.

Month by month in Lexington-Fayette urban county

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 814 hours a year at full output.

Lexington-Fayette urban county against nearby cities

Of 42 Kentucky cities here, Lexington-Fayette urban county has the 21st highest cooling load. The range runs from Versailles at 29,000 BTU/hr to Paducah at 36,900.

Where Lexington-Fayette urban county's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lexington Bluegrass Airport, 8.3 miles from the center of Lexington-Fayette urban county at 962 ft above sea level. That is close enough that the station's summers are Lexington-Fayette urban county's summers.

4 other cities use the same station and get the same climate inputs. The closest to Lexington-Fayette urban county: Nicholasville (12 mi away, 10.1 mi from the station), Winchester (15 mi away, 23 mi from the station), Paris (15 mi away, 21.7 mi from the station), Georgetown (16 mi away, 16.2 mi from the station). Lexington-Fayette urban county sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Lexington-Fayette urban county in late July

At 38.04°N, the noon sun on 21 July stands 72.4° above the horizon over Lexington-Fayette urban county and the day runs 14 h 15 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.

329,437 people live in Lexington-Fayette urban county, the 2nd largest of the 42 Kentucky cities sized on this site. Coordinates used: 38.0407, -84.4583.

Lexington-Fayette urban county AC sizing questions