What size AC for The Dalles, OR? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 31,100 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 35% 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 772 square feet in this climate. For a single room, size by the room: 15.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Dallesport Airport (1.6 mi away). Jul is the hottest month, averaging a high of 88.4°F and a low of 61°F, with about 43 days a year at 90°F or more. That gives a design temperature of 94°F against 75°F inside.

What it costs to run

About 1,083 kWh a year at SEER2 14.3, or roughly $167 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in The Dalles

Of the 31,100 BTU/hr, 13,680 comes through walls, roof and windows on a 94°F afternoon (44%), 13,000 is sun on the house (42%), 2,120 is four people and their appliances, and 2,300 is moisture the coil has to wring out of The Dalles's summer air (7%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 28,800 BTU/hr before the moisture allowance.

Other house sizes in The Dalles

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,300 BTU/hr; a 350 sq ft living room needs about 5,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,400 BTU/hr.

Month by month in The Dalles

Jul alone uses 36% of the year's cooling energy. The unit runs the equivalent of 498 hours a year at full output.

The Dalles against nearby cities

Of 57 Oregon cities here, The Dalles has the 6th highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where The Dalles's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Dallesport Airport, across the line in Washington, 1.6 miles from the center of The Dalles at 234 ft above sea level. That is close enough that the station's summers are The Dalles's summers.

No other city in this set uses Dallesport Airport, so this sizing is The Dalles's alone.

The sun over The Dalles in late July

At 45.60°N, the noon sun on 21 July stands 64.8° above the horizon over The Dalles and the day runs 14 h 59 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.

15,884 people live in The Dalles, the 37th largest of the 57 Oregon cities sized on this site. Coordinates used: 45.5984, -121.1524.

The Dalles AC sizing questions