What size AC for Enumclaw, WA? 2 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Enumclaw 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 Buckley 1 Ne (2.4 mi away). Aug is the hottest month, averaging a high of 76.9°F and a low of 51.5°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 150 kWh a year at SEER2 14.3, or roughly $22 at Washington's average residential rate of 14.42¢ per kWh. Cooling runs 0 months of the year here.

What drives the load in Enumclaw

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 Enumclaw'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 Enumclaw

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 Enumclaw

Jul alone uses 41% of the year's cooling energy. The unit runs the equivalent of 106 hours a year at full output.

Enumclaw against nearby cities

Of 91 Washington cities here, Enumclaw has the 63rd highest cooling load. The range runs from Burlington at 15,700 BTU/hr to Kennewick at 32,900.

Where Enumclaw's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Buckley 1 Ne, 2.4 miles from the center of Enumclaw at 685 ft above sea level. That is close enough that the station's summers are Enumclaw's summers.

No other city in this set uses Buckley 1 Ne, so this sizing is Enumclaw's alone.

The sun over Enumclaw in late July

At 47.20°N, the noon sun on 21 July stands 63.2° above the horizon over Enumclaw and the day runs 15 h 09 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.

13,173 people live in Enumclaw, the 77th largest of the 91 Washington cities sized on this site. Coordinates used: 47.2022, -121.9890.

Enumclaw AC sizing questions