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

What size AC a 2,000 sq ft house in Bay City 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 Saginaw Mbs International Airport (10.6 mi away). Jul is the hottest month, averaging a high of 82.2°F and a low of 61.2°F, with about 9 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 823 kWh a year at SEER2 14.3, or roughly $179 at Michigan's average residential rate of 21.73¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Bay City

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 Bay City'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 Bay City

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 Bay City

Jul alone uses 34% of the year's cooling energy. The unit runs the equivalent of 473 hours a year at full output.

Bay City against nearby cities

Of 90 Michigan cities here, Bay City has the 77th highest cooling load. The range runs from Marquette at 18,700 BTU/hr to Ypsilanti at 28,800.

Where Bay City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Saginaw Mbs International Airport, 10.6 miles from the center of Bay City at 662 ft above sea level. That is close enough that the station's summers are Bay City's summers.

2 other cities use the same station and get the same climate inputs. The closest to Bay City: Saginaw (12 mi away, 9.9 mi from the station), Midland (17 mi away, 10.1 mi from the station). Bay City is farther from the station than 2 of them.

The sun over Bay City in late July

At 43.59°N, the noon sun on 21 July stands 66.8° above the horizon over Bay City and the day runs 14 h 46 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.

32,086 people live in Bay City, the 34th largest of the 90 Michigan cities sized on this site. Coordinates used: 43.5901, -83.8884.

Bay City AC sizing questions