What size AC for Somerville, NJ? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 46% 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 834 square feet in this climate. For a single room, size by the room: 14.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Somerset Airport (4.9 mi away). Jul is the hottest month, averaging a high of 86.2°F and a low of 63°F, with about 23 days a year at 90°F or more. That gives a design temperature of 91°F against 75°F inside.

What it costs to run

About 1,121 kWh a year at SEER2 14.3, or roughly $270 at New Jersey's average residential rate of 24.09¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Somerville

Of the 28,800 BTU/hr, 11,520 comes through walls, roof and windows on a 91°F afternoon (40%), 13,000 is sun on the house (45%), 2,120 is four people and their appliances, and 2,100 is moisture the coil has to wring out of Somerville's summer air (7%).

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 26,640 BTU/hr before the moisture allowance.

Other house sizes in Somerville

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 5,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,600 BTU/hr.

Month by month in Somerville

Jul alone uses 35% of the year's cooling energy. The unit runs the equivalent of 557 hours a year at full output.

Somerville against nearby cities

Of 116 New Jersey cities here, Somerville has the 103rd highest cooling load. The range runs from Hackettstown at 26,400 BTU/hr to Camden at 34,300.

Where Somerville's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Somerset Airport, 4.9 miles from the center of Somerville at 99 ft above sea level. That is close enough that the station's summers are Somerville's summers.

8 other cities use the same station and get the same climate inputs. The closest to Somerville: Manville (2 mi away, 7.1 mi from the station), Bound Brook (4 mi away, 7.9 mi from the station), Middlesex (6 mi away, 9.6 mi from the station), North Plainfield (10 mi away, 12 mi from the station), South Plainfield (10 mi away, 13.8 mi from the station). Somerville sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Somerville in late July

At 40.57°N, the noon sun on 21 July stands 69.8° above the horizon over Somerville 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.

14,428 people live in Somerville, the 73rd largest of the 116 New Jersey cities sized on this site. Coordinates used: 40.5697, -74.6077.

Somerville AC sizing questions