What size AC for Sweet Home, OR? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 24,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 70% 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 971 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 Foster Dam (1.6 mi away). Aug is the hottest month, averaging a high of 82.6°F and a low of 50.3°F, with about 17 days a year at 90°F or more. That gives a design temperature of 87°F against 75°F inside.

What it costs to run

About 293 kWh a year at SEER2 14.3, or roughly $45 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Sweet Home

Of the 24,700 BTU/hr, 8,640 comes through walls, roof and windows on a 87°F afternoon (35%), 13,000 is sun on the house (53%), 2,120 is four people and their appliances, and 1,000 is moisture the coil has to wring out of Sweet Home's summer air (4%).

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 23,760 BTU/hr before the moisture allowance.

Other house sizes in Sweet Home

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 Sweet Home

Aug alone uses 38% of the year's cooling energy. The unit runs the equivalent of 169 hours a year at full output.

Sweet Home against nearby cities

Of 57 Oregon cities here, Sweet Home has the 51st highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where Sweet Home's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Foster Dam, 1.6 miles from the center of Sweet Home at 550 ft above sea level. That is close enough that the station's summers are Sweet Home's summers.

No other city in this set uses Foster Dam, so this sizing is Sweet Home's alone.

The sun over Sweet Home in late July

At 44.40°N, the noon sun on 21 July stands 66.0° above the horizon over Sweet Home and the day runs 14 h 51 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.

10,265 people live in Sweet Home, the 53rd largest of the 57 Oregon cities sized on this site. Coordinates used: 44.4040, -122.7015.

Sweet Home AC sizing questions