What size AC for Bemidji, MN? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 22,600 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 86% 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 1,064 square feet in this climate. For a single room, size by the room: 11.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Cass Lake (14.4 mi away). Jul is the hottest month, averaging a high of 79.1°F and a low of 58°F, with about 4 days a year at 90°F or more. That gives a design temperature of 83°F against 75°F inside.

What it costs to run

About 489 kWh a year at SEER2 14.3, or roughly $80 at Minnesota's average residential rate of 16.44¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Bemidji

Of the 22,600 BTU/hr, 5,760 comes through walls, roof and windows on a 83°F afternoon (25%), 13,000 is sun on the house (58%), 2,120 is four people and their appliances, and 1,700 is moisture the coil has to wring out of Bemidji'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 20,880 BTU/hr before the moisture allowance.

Other house sizes in Bemidji

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,700 BTU/hr; a 350 sq ft living room needs about 4,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,800 BTU/hr.

Month by month in Bemidji

Jul alone uses 39% of the year's cooling energy. The unit runs the equivalent of 310 hours a year at full output.

Bemidji against nearby cities

Of 103 Minnesota cities here, Bemidji has the 97th highest cooling load. The range runs from Hibbing at 20,200 BTU/hr to Winona at 29,000.

Where Bemidji's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Cass Lake, 14.4 miles from the center of Bemidji at 1,296 ft above sea level. That is close enough that the station's summers are Bemidji's summers.

No other city in this set uses Cass Lake, so this sizing is Bemidji's alone.

The sun over Bemidji in late July

At 47.49°N, the noon sun on 21 July stands 62.9° above the horizon over Bemidji and the day runs 15 h 11 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.

15,733 people live in Bemidji, the 72nd largest of the 103 Minnesota cities sized on this site. Coordinates used: 47.4870, -94.8827.

Bemidji AC sizing questions