What size AC for Bellingham, WA? 1.5 tons for 2,000 sq ft

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

1.5 tons central AC or heat pump, about 17,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 144% 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 1,394 square feet in this climate. For a single room, size by the room: 8.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Bellingham International Airport (4.5 mi away). Aug is the hottest month, averaging a high of 73.1°F and a low of 54.7°F, with about 0 days a year at 90°F or more. That gives a design temperature of 77°F against 75°F inside.

What it costs to run

About 95 kWh a year at SEER2 14.3, or roughly $14 at Washington's average residential rate of 14.42¢ per kWh. Cooling runs 0 months of the year here.

What drives the load in Bellingham

Of the 17,200 BTU/hr, 1,440 comes through walls, roof and windows on a 77°F afternoon (8%), 13,000 is sun on the house (76%), 2,120 is four people and their appliances, and 700 is moisture the coil has to wring out of Bellingham'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 16,560 BTU/hr before the moisture allowance.

Other house sizes in Bellingham

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 1,300 BTU/hr; a 350 sq ft living room needs about 3,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 5,200 BTU/hr.

Month by month in Bellingham

Jul alone uses 41% of the year's cooling energy. The unit runs the equivalent of 78 hours a year at full output.

Bellingham against nearby cities

Of 91 Washington cities here, Bellingham has the 74th highest cooling load. The range runs from Burlington at 15,700 BTU/hr to Kennewick at 32,900.

Where Bellingham's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Bellingham International Airport, 4.5 miles from the center of Bellingham at 150 ft above sea level. That is close enough that the station's summers are Bellingham's summers.

2 other cities use the same station and get the same climate inputs. The closest to Bellingham: Ferndale (9 mi away, 4.4 mi from the station), Lynden (14 mi away, 11.1 mi from the station). Bellingham is farther from the station than 1 of them.

The sun over Bellingham in late July

At 48.75°N, the noon sun on 21 July stands 61.6° above the horizon over Bellingham and the day runs 15 h 21 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.

95,860 people live in Bellingham, the 12th largest of the 91 Washington cities sized on this site. Coordinates used: 48.7534, -122.4702.

Bellingham AC sizing questions