What size AC for Groton, CT? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 24,800 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 966 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 Groton New London Airport (1 mi away). Jul is the hottest month, averaging a high of 79.8°F and a low of 64.8°F, with about 2 days a year at 90°F or more. That gives a design temperature of 84°F against 75°F inside.

What it costs to run

About 845 kWh a year at SEER2 14.3, or roughly $232 at Connecticut's average residential rate of 27.47¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Groton

Of the 24,800 BTU/hr, 6,480 comes through walls, roof and windows on a 84°F afternoon (26%), 13,000 is sun on the house (52%), 2,120 is four people and their appliances, and 3,200 is moisture the coil has to wring out of Groton's summer air (13%).

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 21,600 BTU/hr before the moisture allowance.

Other house sizes in Groton

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 Groton

Jul alone uses 38% of the year's cooling energy. The unit runs the equivalent of 486 hours a year at full output.

Groton against nearby cities

Of 21 Connecticut cities here, Groton has the lowest cooling load. The range runs from Groton at 24,800 BTU/hr to Hartford at 29,000.

Where Groton's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Groton New London Airport, 1 miles from the center of Groton at 8 ft above sea level. That is close enough that the station's summers are Groton's summers.

1 other city uses the same station and get the same climate inputs. The closest to Groton: New London (2 mi away, 2.5 mi from the station). Groton sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Groton in late July

At 41.33°N, the noon sun on 21 July stands 69.1° above the horizon over Groton and the day runs 14 h 33 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.

10,160 people live in Groton, the 21st largest of the 21 Connecticut cities sized on this site. Coordinates used: 41.3251, -72.0669.

Groton AC sizing questions