What size AC for Culpeper, VA? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 46% 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 2.5 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 834 square feet in this climate. For a single room, size by the room: 14.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Boston 4 Se (7.4 mi away). Jul is the hottest month, averaging a high of 85.9°F and a low of 63.8°F, with about 22 days a year at 90°F or more. That gives a design temperature of 91°F against 75°F inside.

What it costs to run

About 1,222 kWh a year at SEER2 14.3, or roughly $207 at Virginia's average residential rate of 16.95¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Culpeper

Of the 28,800 BTU/hr, 11,520 comes through walls, roof and windows on a 91°F afternoon (40%), 13,000 is sun on the house (45%), 2,120 is four people and their appliances, and 2,100 is moisture the coil has to wring out of Culpeper's summer air (7%).

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 26,640 BTU/hr before the moisture allowance.

Other house sizes in Culpeper

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,200 BTU/hr; a 350 sq ft living room needs about 5,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,600 BTU/hr.

Month by month in Culpeper

Jul alone uses 33% of the year's cooling energy. The unit runs the equivalent of 607 hours a year at full output.

Culpeper against nearby cities

Of 39 Virginia cities here, Culpeper has the 34th highest cooling load. The range runs from Christiansburg at 24,900 BTU/hr to Chesapeake at 42,100.

Where Culpeper's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Boston 4 Se, 7.4 miles from the center of Culpeper at 590 ft above sea level. That is close enough that the station's summers are Culpeper's summers.

No other city in this set uses Boston 4 Se, so this sizing is Culpeper's alone.

The sun over Culpeper in late July

At 38.47°N, the noon sun on 21 July stands 71.9° above the horizon over Culpeper and the day runs 14 h 18 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.

21,464 people live in Culpeper, the 28th largest of the 39 Virginia cities sized on this site. Coordinates used: 38.4703, -77.9998.

Culpeper AC sizing questions