What size AC for Norfolk, VA? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 37,400 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.1 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 641 square feet in this climate. For a single room, size by the room: 18.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Norfolk NAS (2.7 mi away). Jul is the hottest month, averaging a high of 88.7°F and a low of 72.6°F, with about 42 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 2,863 kWh a year at SEER2 14.3, or roughly $485 at Virginia's average residential rate of 16.95¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Norfolk

Of the 37,400 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (37%), 13,000 is sun on the house (35%), 2,120 is four people and their appliances, and 8,600 is moisture the coil has to wring out of Norfolk'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 28,800 BTU/hr before the moisture allowance.

Other house sizes in Norfolk

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,800 BTU/hr; a 350 sq ft living room needs about 6,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,200 BTU/hr.

Month by month in Norfolk

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 1,094 hours a year at full output.

Norfolk against nearby cities

Of 39 Virginia cities here, Norfolk has the 4th highest cooling load. The range runs from Christiansburg at 24,900 BTU/hr to Chesapeake at 42,100.

Where Norfolk's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Norfolk NAS, 2.7 miles from the center of Norfolk at 17 ft above sea level. That is close enough that the station's summers are Norfolk's summers.

1 other city uses the same station and get the same climate inputs. The closest to Norfolk: Portsmouth (8 mi away, 6.6 mi from the station). Norfolk sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Norfolk in late July

At 36.92°N, the noon sun on 21 July stands 73.5° above the horizon over Norfolk and the day runs 14 h 10 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.

231,105 people live in Norfolk, the 4th largest of the 39 Virginia cities sized on this site. Coordinates used: 36.9230, -76.2446.

Norfolk AC sizing questions