What size AC for Sanford, ME? 2 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Sanford 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 Rochester Skyhaven Airport (13 mi away). Jul is the hottest month, averaging a high of 81.9°F and a low of 59.6°F, with about 11 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 661 kWh a year at SEER2 14.3, or roughly $200 at Maine's average residential rate of 30.23¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Sanford

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 Sanford'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 Sanford

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 Sanford

Jul alone uses 38% of the year's cooling energy. The unit runs the equivalent of 380 hours a year at full output.

Sanford against nearby cities

Of 11 Maine cities here, Sanford has the highest cooling load. The range runs from Waterville at 23,300 BTU/hr to Sanford at 24,900.

Where Sanford's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Rochester Skyhaven Airport, across the line in New Hampshire, 13 miles from the center of Sanford at 329 ft above sea level. That is close enough that the station's summers are Sanford's summers.

2 other cities use the same station and get the same climate inputs. The closest to Sanford: Somersworth (13 mi away, 2.6 mi from the station), Rochester (14 mi away, 3 mi from the station). Sanford is farther from the station than 2 of them.

The sun over Sanford in late July

At 43.42°N, the noon sun on 21 July stands 67.0° above the horizon over Sanford 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.

22,497 people live in Sanford, the 6th largest of the 11 Maine cities sized on this site. Coordinates used: 43.4241, -70.7579.

Sanford AC sizing questions