What size AC for Forest Lake, MN? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 26,400 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 59% 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 908 square feet in this climate. For a single room, size by the room: 13.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Forest Lake 5ne (6.5 mi away). Jul is the hottest month, averaging a high of 83.4°F and a low of 60.2°F, with about 14 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 799 kWh a year at SEER2 14.3, or roughly $131 at Minnesota's average residential rate of 16.44¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Forest Lake

Of the 26,400 BTU/hr, 9,360 comes through walls, roof and windows on a 88°F afternoon (35%), 13,000 is sun on the house (49%), 2,120 is four people and their appliances, and 2,000 is moisture the coil has to wring out of Forest Lake'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 24,480 BTU/hr before the moisture allowance.

Other house sizes in Forest Lake

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,000 BTU/hr; a 350 sq ft living room needs about 4,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,900 BTU/hr.

Month by month in Forest Lake

Jul alone uses 36% of the year's cooling energy. The unit runs the equivalent of 432 hours a year at full output.

Forest Lake against nearby cities

Of 103 Minnesota cities here, Forest Lake has the 61st highest cooling load. The range runs from Hibbing at 20,200 BTU/hr to Winona at 29,000.

Where Forest Lake's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Forest Lake 5ne, 6.5 miles from the center of Forest Lake at 905 ft above sea level. That is close enough that the station's summers are Forest Lake's summers.

No other city in this set uses Forest Lake 5ne, so this sizing is Forest Lake's alone.

The sun over Forest Lake in late July

At 45.25°N, the noon sun on 21 July stands 65.1° above the horizon over Forest Lake and the day runs 14 h 56 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.

20,700 people live in Forest Lake, the 60th largest of the 103 Minnesota cities sized on this site. Coordinates used: 45.2508, -92.9669.

Forest Lake AC sizing questions