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

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

2 tons central AC or heat pump, about 24,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 75% 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 1,002 square feet in this climate. For a single room, size by the room: 12 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Springfield Hartness State Airport (9.9 mi away). Jul is the hottest month, averaging a high of 81.4°F and a low of 57.2°F, with about 8 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 474 kWh a year at SEER2 14.3, or roughly $128 at New Hampshire's average residential rate of 26.91¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Claremont

Of the 24,000 BTU/hr, 7,920 comes through walls, roof and windows on a 86°F afternoon (33%), 13,000 is sun on the house (54%), 2,120 is four people and their appliances, and 900 is moisture the coil has to wring out of Claremont's summer air (4%).

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 Claremont

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,800 BTU/hr; a 350 sq ft living room needs about 4,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,200 BTU/hr.

Month by month in Claremont

Jul alone uses 40% of the year's cooling energy. The unit runs the equivalent of 283 hours a year at full output.

Claremont against nearby cities

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

Where Claremont's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Springfield Hartness State Airport, across the line in Vermont, 9.9 miles from the center of Claremont at 568 ft above sea level. That is close enough that the station's summers are Claremont's summers.

No other city in this set uses Springfield Hartness State Airport, so this sizing is Claremont's alone.

The sun over Claremont in late July

At 43.39°N, the noon sun on 21 July stands 67.0° above the horizon over Claremont and the day runs 14 h 45 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.

13,105 people live in Claremont, the 10th largest of the 11 New Hampshire cities sized on this site. Coordinates used: 43.3865, -72.3345.

Claremont AC sizing questions