What size AC for Grants Pass, OR? 2 tons for 2,000 sq ft

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

2 tons central AC or heat pump, about 20,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 108% 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 1,187 square feet in this climate. For a single room, size by the room: 10.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Sexton Summit (11.7 mi away). Jul is the hottest month, averaging a high of 76.7°F and a low of 53.1°F, with about 4 days a year at 90°F or more. That gives a design temperature of 81°F against 75°F inside.

What it costs to run

About 346 kWh a year at SEER2 14.3, or roughly $54 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Grants Pass

Of the 20,200 BTU/hr, 4,320 comes through walls, roof and windows on a 81°F afternoon (21%), 13,000 is sun on the house (64%), 2,120 is four people and their appliances, and 800 is moisture the coil has to wring out of Grants Pass'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 19,440 BTU/hr before the moisture allowance.

Other house sizes in Grants Pass

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,500 BTU/hr; a 350 sq ft living room needs about 3,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 6,100 BTU/hr.

Month by month in Grants Pass

Aug alone uses 34% of the year's cooling energy. The unit runs the equivalent of 245 hours a year at full output.

Grants Pass against nearby cities

Of 57 Oregon cities here, Grants Pass has the 53rd highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where Grants Pass's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Sexton Summit, 11.7 miles from the center of Grants Pass at 3,841 ft above sea level. That is close enough that the station's summers are Grants Pass's summers.

No other city in this set uses Sexton Summit, so this sizing is Grants Pass's alone.

The sun over Grants Pass in late July

At 42.43°N, the noon sun on 21 July stands 68.0° above the horizon over Grants Pass 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.

39,468 people live in Grants Pass, the 14th largest of the 57 Oregon cities sized on this site. Coordinates used: 42.4323, -123.3318.

Grants Pass AC sizing questions