What size AC for Sedro-Woolley, WA? 1.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Sedro-Woolley needs

1.5 tons central AC or heat pump, about 18,700 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 124% 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 1.5 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 1,282 square feet in this climate. For a single room, size by the room: 9.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Sedro-Woolley (1.1 mi away). Aug is the hottest month, averaging a high of 75.2°F and a low of 52.9°F, with about 1 day a year at 90°F or more. That gives a design temperature of 79°F against 75°F inside.

What it costs to run

About 109 kWh a year at SEER2 14.3, or roughly $16 at Washington's average residential rate of 14.42¢ per kWh. Cooling runs 0 months of the year here.

What drives the load in Sedro-Woolley

Of the 18,700 BTU/hr, 2,880 comes through walls, roof and windows on a 79°F afternoon (15%), 13,000 is sun on the house (70%), 2,120 is four people and their appliances, and 700 is moisture the coil has to wring out of Sedro-Woolley'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 18,000 BTU/hr before the moisture allowance.

Other house sizes in Sedro-Woolley

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,400 BTU/hr; a 350 sq ft living room needs about 3,300 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 5,600 BTU/hr.

Month by month in Sedro-Woolley

Jul alone uses 39% of the year's cooling energy. The unit runs the equivalent of 83 hours a year at full output.

Sedro-Woolley against nearby cities

Of 91 Washington cities here, Sedro-Woolley has the 72nd highest cooling load. The range runs from Burlington at 15,700 BTU/hr to Kennewick at 32,900.

Where Sedro-Woolley's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Sedro-Woolley, 1.1 miles from the center of Sedro-Woolley at 52 ft above sea level. That is close enough that the station's summers are Sedro-Woolley's summers.

No other city in this set uses Sedro-Woolley, so this sizing is Sedro-Woolley's alone.

The sun over Sedro-Woolley in late July

At 48.51°N, the noon sun on 21 July stands 61.9° above the horizon over Sedro-Woolley and the day runs 15 h 19 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.

13,215 people live in Sedro-Woolley, the 76th largest of the 91 Washington cities sized on this site. Coordinates used: 48.5114, -122.2322.

Sedro-Woolley AC sizing questions