What size AC for Klamath Falls, OR? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 27,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 52% 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 866 square feet in this climate. For a single room, size by the room: 13.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Klamath Falls International Airport (5.7 mi away). Jul is the hottest month, averaging a high of 86.3°F and a low of 47.8°F, with about 18 days a year at 90°F or more. That gives a design temperature of 91°F against 75°F inside.

What it costs to run

About 272 kWh a year at SEER2 14.3, or roughly $42 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Klamath Falls

Of the 27,700 BTU/hr, 11,520 comes through walls, roof and windows on a 91°F afternoon (42%), 13,000 is sun on the house (47%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Klamath Falls'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 26,640 BTU/hr before the moisture allowance.

Other house sizes in Klamath Falls

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 8,300 BTU/hr.

Month by month in Klamath Falls

Jul alone uses 48% of the year's cooling energy. The unit runs the equivalent of 140 hours a year at full output.

Klamath Falls against nearby cities

Of 57 Oregon cities here, Klamath Falls has the 14th highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where Klamath Falls's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Klamath Falls International Airport, 5.7 miles from the center of Klamath Falls at 4,083 ft above sea level. That is close enough that the station's summers are Klamath Falls's summers.

No other city in this set uses Klamath Falls International Airport, so this sizing is Klamath Falls's alone.

The sun over Klamath Falls in late July

At 42.22°N, the noon sun on 21 July stands 68.2° above the horizon over Klamath Falls and the day runs 14 h 38 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.

22,174 people live in Klamath Falls, the 27th largest of the 57 Oregon cities sized on this site. Coordinates used: 42.2188, -121.7787.

Klamath Falls AC sizing questions