What size AC for Concord, NH? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 25,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 64% 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 935 square feet in this climate. For a single room, size by the room: 12.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Concord Asos (3.5 mi away). Jul is the hottest month, averaging a high of 83°F and a low of 59.2°F, with about 14 days a year at 90°F or more. That gives a design temperature of 87°F against 75°F inside.

What it costs to run

About 689 kWh a year at SEER2 14.3, or roughly $185 at New Hampshire's average residential rate of 26.91¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Concord

Of the 25,700 BTU/hr, 8,640 comes through walls, roof and windows on a 87°F afternoon (34%), 13,000 is sun on the house (51%), 2,120 is four people and their appliances, and 1,900 is moisture the coil has to wring out of Concord'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 23,760 BTU/hr before the moisture allowance.

Other house sizes in Concord

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 4,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,700 BTU/hr.

Month by month in Concord

Jul alone uses 38% of the year's cooling energy. The unit runs the equivalent of 384 hours a year at full output.

Concord against nearby cities

Of 11 New Hampshire cities here, Concord has the 3rd highest cooling load. The range runs from Claremont at 24,000 BTU/hr to Manchester at 27,200.

Where Concord's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Concord Asos, 3.5 miles from the center of Concord at 338 ft above sea level. That is close enough that the station's summers are Concord's summers.

No other city in this set uses Concord Asos, so this sizing is Concord's alone.

The sun over Concord in late July

At 43.23°N, the noon sun on 21 July stands 67.2° above the horizon over Concord and the day runs 14 h 44 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.

44,674 people live in Concord, the 3rd largest of the 11 New Hampshire cities sized on this site. Coordinates used: 43.2325, -71.5613.

Concord AC sizing questions