What size AC for Lexington, NC? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 33,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 27% 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 725 square feet in this climate. For a single room, size by the room: 16.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Lexington (3.4 mi away). Jul is the hottest month, averaging a high of 89.1°F and a low of 67.1°F, with about 39 days a year at 90°F or more. That gives a design temperature of 94°F against 75°F inside.

What it costs to run

About 2,022 kWh a year at SEER2 14.3, or roughly $302 at North Carolina's average residential rate of 14.94¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Lexington

Of the 33,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (41%), 13,000 is sun on the house (39%), 2,120 is four people and their appliances, and 4,300 is moisture the coil has to wring out of Lexington's summer air (13%).

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 28,800 BTU/hr before the moisture allowance.

Other house sizes in Lexington

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,500 BTU/hr; a 350 sq ft living room needs about 5,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,000 BTU/hr.

Month by month in Lexington

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 873 hours a year at full output.

Lexington against nearby cities

Of 91 North Carolina cities here, Lexington has the 81st highest cooling load. The range runs from Boone at 21,700 BTU/hr to Lumberton at 40,200.

Where Lexington's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Lexington, 3.4 miles from the center of Lexington at 760 ft above sea level. That is close enough that the station's summers are Lexington's summers.

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

The sun over Lexington in late July

At 35.80°N, the noon sun on 21 July stands 74.6° above the horizon over Lexington and the day runs 14 h 04 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.

19,904 people live in Lexington, the 52nd largest of the 91 North Carolina cities sized on this site. Coordinates used: 35.7972, -80.2743.

Lexington AC sizing questions