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

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

3 tons central AC or heat pump, about 33,400 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 26% 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 719 square feet in this climate. For a single room, size by the room: 16.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Langley AFB (4 mi away). Jul is the hottest month, averaging a high of 87.3°F and a low of 71.2°F, with about 30 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 2,348 kWh a year at SEER2 14.3, or roughly $398 at Virginia's average residential rate of 16.95¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Poquoson

Of the 33,400 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (37%), 13,000 is sun on the house (39%), 2,120 is four people and their appliances, and 6,000 is moisture the coil has to wring out of Poquoson's summer air (18%).

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 Poquoson

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 Poquoson

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 1,006 hours a year at full output.

Poquoson against nearby cities

Of 39 Virginia cities here, Poquoson has the 15th highest cooling load. The range runs from Christiansburg at 24,900 BTU/hr to Chesapeake at 42,100.

Where Poquoson's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Langley AFB, 4 miles from the center of Poquoson at 10 ft above sea level. That is close enough that the station's summers are Poquoson's summers.

1 other city uses the same station and get the same climate inputs. The closest to Poquoson: Hampton (6 mi away, 3.8 mi from the station). Poquoson is farther from the station than 1 of them.

The sun over Poquoson in late July

At 37.13°N, the noon sun on 21 July stands 73.3° above the horizon over Poquoson and the day runs 14 h 11 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.

12,854 people live in Poquoson, the 38th largest of the 39 Virginia cities sized on this site. Coordinates used: 37.1284, -76.3035.

Poquoson AC sizing questions