What size AC for Williamsburg, VA? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 35,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 20% 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 683 square feet in this climate. For a single room, size by the room: 17.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Newport News International Airport (15.1 mi away). Jul is the hottest month, averaging a high of 88.2°F and a low of 70.3°F, with about 43 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 2,303 kWh a year at SEER2 14.3, or roughly $390 at Virginia's average residential rate of 16.95¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Williamsburg

Of the 35,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (39%), 13,000 is sun on the house (37%), 2,120 is four people and their appliances, and 6,300 is moisture the coil has to wring out of Williamsburg'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 28,800 BTU/hr before the moisture allowance.

Other house sizes in Williamsburg

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,600 BTU/hr; a 350 sq ft living room needs about 6,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,600 BTU/hr.

Month by month in Williamsburg

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 937 hours a year at full output.

Williamsburg against nearby cities

Of 39 Virginia cities here, Williamsburg has the 11th highest cooling load. The range runs from Christiansburg at 24,900 BTU/hr to Chesapeake at 42,100.

Where Williamsburg's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Newport News International Airport, 15.1 miles from the center of Williamsburg at 36 ft above sea level. That is close enough that the station's summers are Williamsburg's summers.

1 other city uses the same station and get the same climate inputs. The closest to Williamsburg: Newport News (17 mi away, 4.2 mi from the station). Williamsburg is farther from the station than 1 of them.

The sun over Williamsburg in late July

At 37.27°N, the noon sun on 21 July stands 73.1° above the horizon over Williamsburg and the day runs 14 h 12 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.

16,030 people live in Williamsburg, the 34th largest of the 39 Virginia cities sized on this site. Coordinates used: 37.2695, -76.7082.

Williamsburg AC sizing questions