What size AC for Rockville Centre, NY? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 29,900 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 41% 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 804 square feet in this climate. For a single room, size by the room: 14.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Jfk International Airport (6.8 mi away). Jul is the hottest month, averaging a high of 83.6°F and a low of 68.7°F, with about 11 days a year at 90°F or more. That gives a design temperature of 88°F against 75°F inside.

What it costs to run

About 1,499 kWh a year at SEER2 14.3, or roughly $438 at New York's average residential rate of 29.26¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Rockville Centre

Of the 29,900 BTU/hr, 9,360 comes through walls, roof and windows on a 88°F afternoon (31%), 13,000 is sun on the house (43%), 2,120 is four people and their appliances, and 5,400 is moisture the coil has to wring out of Rockville Centre'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 24,480 BTU/hr before the moisture allowance.

Other house sizes in Rockville Centre

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 5,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,900 BTU/hr.

Month by month in Rockville Centre

Jul alone uses 34% of the year's cooling energy. The unit runs the equivalent of 718 hours a year at full output.

Rockville Centre against nearby cities

Of 90 New York cities here, Rockville Centre has the 12th highest cooling load. The range runs from Gloversville at 20,200 BTU/hr to Spring Valley at 33,400.

Where Rockville Centre's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Jfk International Airport, 6.8 miles from the center of Rockville Centre at 9 ft above sea level. That is close enough that the station's summers are Rockville Centre's summers.

10 other cities use the same station and get the same climate inputs. The closest to Rockville Centre: Lynbrook (2 mi away, 4.9 mi from the station), East Rockaway (2 mi away, 5.1 mi from the station), Freeport (3 mi away, 9.4 mi from the station), Hempstead (3 mi away, 8.8 mi from the station), Valley Stream (4 mi away, 3.6 mi from the station). Rockville Centre is farther from the station than 5 of them.

The sun over Rockville Centre in late July

At 40.66°N, the noon sun on 21 July stands 69.7° above the horizon over Rockville Centre and the day runs 14 h 29 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.

25,718 people live in Rockville Centre, the 37th largest of the 90 New York cities sized on this site. Coordinates used: 40.6640, -73.6380.

Rockville Centre AC sizing questions