What size AC for Alpena, MI? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 21,000 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 100% 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 1,143 square feet in this climate. For a single room, size by the room: 10.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Alpena Wwtp (1.2 mi away). Jul is the hottest month, averaging a high of 77.1°F and a low of 59.4°F, with about 4 days a year at 90°F or more. That gives a design temperature of 81°F against 75°F inside.

What it costs to run

About 439 kWh a year at SEER2 14.3, or roughly $95 at Michigan's average residential rate of 21.73¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Alpena

Of the 21,000 BTU/hr, 4,320 comes through walls, roof and windows on a 81°F afternoon (21%), 13,000 is sun on the house (62%), 2,120 is four people and their appliances, and 1,600 is moisture the coil has to wring out of Alpena's summer air (8%).

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 19,440 BTU/hr before the moisture allowance.

Other house sizes in Alpena

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,600 BTU/hr; a 350 sq ft living room needs about 3,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,300 BTU/hr.

Month by month in Alpena

Jul alone uses 39% of the year's cooling energy. The unit runs the equivalent of 299 hours a year at full output.

Alpena against nearby cities

Of 90 Michigan cities here, Alpena has the 87th highest cooling load. The range runs from Marquette at 18,700 BTU/hr to Ypsilanti at 28,800.

Where Alpena's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Alpena Wwtp, 1.2 miles from the center of Alpena at 590 ft above sea level. That is close enough that the station's summers are Alpena's summers.

No other city in this set uses Alpena Wwtp, so this sizing is Alpena's alone.

The sun over Alpena in late July

At 45.07°N, the noon sun on 21 July stands 65.3° above the horizon over Alpena and the day runs 14 h 55 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.

10,116 people live in Alpena, the 90th largest of the 90 Michigan cities sized on this site. Coordinates used: 45.0745, -83.4436.

Alpena AC sizing questions