What size AC for Jacksonville, NC? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 38,400 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.2 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 625 square feet in this climate. For a single room, size by the room: 19.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at New River Mcaf (3 mi away). Jul is the hottest month, averaging a high of 89.3°F and a low of 72.5°F, with about 44 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 3,177 kWh a year at SEER2 14.3, or roughly $475 at North Carolina's average residential rate of 14.94¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Jacksonville

Of the 38,400 BTU/hr, 14,400 comes through walls, roof and windows on a 95°F afternoon (38%), 13,000 is sun on the house (34%), 2,120 is four people and their appliances, and 8,900 is moisture the coil has to wring out of Jacksonville's summer air (23%).

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 Jacksonville

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,900 BTU/hr; a 350 sq ft living room needs about 6,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,500 BTU/hr.

Month by month in Jacksonville

Jul alone uses 24% of the year's cooling energy. The unit runs the equivalent of 1,184 hours a year at full output.

Jacksonville against nearby cities

Of 91 North Carolina cities here, Jacksonville has the 9th highest cooling load. The range runs from Boone at 21,700 BTU/hr to Lumberton at 40,200.

Where Jacksonville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is New River Mcaf, 3 miles from the center of Jacksonville at 26 ft above sea level. That is close enough that the station's summers are Jacksonville's summers.

No other city in this set uses New River Mcaf, so this sizing is Jacksonville's alone.

The sun over Jacksonville in late July

At 34.73°N, the noon sun on 21 July stands 75.7° above the horizon over Jacksonville and the day runs 13 h 60 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.

70,840 people live in Jacksonville, the 15th largest of the 91 North Carolina cities sized on this site. Coordinates used: 34.7297, -77.3937.

Jacksonville AC sizing questions