What size AC for Smyrna, DE? 3 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Smyrna 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 Wilmington New Castle County Airport (26.2 mi away). Jul is the hottest month, averaging a high of 86.8°F and a low of 68.3°F, with about 22 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 1,811 kWh a year at SEER2 14.3, or roughly $326 at Delaware's average residential rate of 17.98¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Smyrna

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 Smyrna'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 Smyrna

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 Smyrna

Jul alone uses 32% of the year's cooling energy. The unit runs the equivalent of 776 hours a year at full output.

Smyrna against nearby cities

Of 6 Delaware cities here, Smyrna has the lowest cooling load. The range runs from Smyrna at 33,400 BTU/hr to Milford at 34,300.

Where Smyrna's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Wilmington New Castle County Airport, 26.2 miles from the center of Smyrna at 74 ft above sea level. That is a long way for a weather station, so treat the design day as approximate: a city on the coast side or the high side of the station can run several degrees different.

4 other cities use the same station and get the same climate inputs. The closest to Smyrna: Middletown (12 mi away, 17 mi from the station), Elkton (24 mi away, 12.4 mi from the station), Newark (28 mi away, 8.1 mi from the station), Wilmington (31 mi away, 5.8 mi from the station). Smyrna is farther from the station than 4 of them.

The sun over Smyrna in late July

At 39.30°N, the noon sun on 21 July stands 71.1° above the horizon over Smyrna and the day runs 14 h 22 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.

13,326 people live in Smyrna, the 6th largest of the 6 Delaware cities sized on this site. Coordinates used: 39.2953, -75.6087.

Smyrna AC sizing questions