What size AC for Braintree Town, MA? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 24,900 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 69% 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 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 965 square feet in this climate. For a single room, size by the room: 12.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Blue Hill Lcd (5.7 mi away). Jul is the hottest month, averaging a high of 81.7°F and a low of 62.7°F, with about 10 days a year at 90°F or more. That gives a design temperature of 86°F against 75°F inside.

What it costs to run

About 818 kWh a year at SEER2 14.3, or roughly $247 at Massachusetts's average residential rate of 30.19¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Braintree Town

Of the 24,900 BTU/hr, 7,920 comes through walls, roof and windows on a 86°F afternoon (32%), 13,000 is sun on the house (52%), 2,120 is four people and their appliances, and 1,800 is moisture the coil has to wring out of Braintree Town'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 23,040 BTU/hr before the moisture allowance.

Other house sizes in Braintree Town

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,900 BTU/hr; a 350 sq ft living room needs about 4,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,400 BTU/hr.

Month by month in Braintree Town

Jul alone uses 37% of the year's cooling energy. The unit runs the equivalent of 470 hours a year at full output.

Braintree Town against nearby cities

Of 58 Massachusetts cities here, Braintree Town has the 52nd highest cooling load. The range runs from Pittsfield at 22,600 BTU/hr to Framingham at 28,000.

Where Braintree Town's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Blue Hill Lcd, 5.7 miles from the center of Braintree Town at 625 ft above sea level. That is close enough that the station's summers are Braintree Town's summers.

5 other cities use the same station and get the same climate inputs. The closest to Braintree Town: Weymouth Town (3 mi away, 8.7 mi from the station), Randolph Town (3 mi away, 3.9 mi from the station), Quincy (4 mi away, 6.3 mi from the station), Brockton (9 mi away, 10.1 mi from the station), Newton (14 mi away, 9.6 mi from the station). Braintree Town is farther from the station than 1 of them.

The sun over Braintree Town in late July

At 42.21°N, the noon sun on 21 July stands 68.2° above the horizon over Braintree Town and the day runs 14 h 38 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. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

39,134 people live in Braintree Town, the 38th largest of the 58 Massachusetts cities sized on this site. Coordinates used: 42.2062, -71.0023.

Braintree Town AC sizing questions