What size AC for Royal Oak, MI? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 49% 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 2.5 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 853 square feet in this climate. For a single room, size by the room: 14.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Detroit City Airport (10.1 mi away). Jul is the hottest month, averaging a high of 83.5°F and a low of 64.9°F, with about 13 days a year at 90°F or more. That gives a design temperature of 88°F against 75°F inside.

What it costs to run

About 1,187 kWh a year at SEER2 14.3, or roughly $258 at Michigan's average residential rate of 21.73¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Royal Oak

Of the 28,200 BTU/hr, 9,360 comes through walls, roof and windows on a 88°F afternoon (33%), 13,000 is sun on the house (46%), 2,120 is four people and their appliances, and 3,700 is moisture the coil has to wring out of Royal Oak's summer air (13%).

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 24,480 BTU/hr before the moisture allowance.

Other house sizes in Royal Oak

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,100 BTU/hr; a 350 sq ft living room needs about 4,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,500 BTU/hr.

Month by month in Royal Oak

Jul alone uses 34% of the year's cooling energy. The unit runs the equivalent of 603 hours a year at full output.

Royal Oak against nearby cities

Of 90 Michigan cities here, Royal Oak has the 12th highest cooling load. The range runs from Marquette at 18,700 BTU/hr to Ypsilanti at 28,800.

Where Royal Oak's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Detroit City Airport, 10.1 miles from the center of Royal Oak at 623 ft above sea level. That is close enough that the station's summers are Royal Oak's summers.

17 other cities use the same station and get the same climate inputs. The closest to Royal Oak: Berkley (2 mi away, 11 mi from the station), Clawson (2 mi away, 11.5 mi from the station), Madison Heights (3 mi away, 8.4 mi from the station), Oak Park (3 mi away, 9.7 mi from the station), Ferndale (4 mi away, 7.2 mi from the station). Royal Oak is farther from the station than 13 of them.

The sun over Royal Oak in late July

At 42.51°N, the noon sun on 21 July stands 67.9° above the horizon over Royal Oak and the day runs 14 h 39 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.

58,251 people live in Royal Oak, the 21st largest of the 90 Michigan cities sized on this site. Coordinates used: 42.5078, -83.1539.

Royal Oak AC sizing questions