What size AC for Durango, CO? 2.5 tons for 2,000 sq ft

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

2.5 tons central AC or heat pump, about 28,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 48% 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 843 square feet in this climate. For a single room, size by the room: 14.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Durango La Plata County Airport (10.5 mi away). Jul is the hottest month, averaging a high of 86.8°F and a low of 52.3°F, with about 22 days a year at 90°F or more. That gives a design temperature of 92°F against 75°F inside.

What it costs to run

About 365 kWh a year at SEER2 14.3, or roughly $61 at Colorado's average residential rate of 16.8¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Durango

Of the 28,500 BTU/hr, 12,240 comes through walls, roof and windows on a 92°F afternoon (43%), 13,000 is sun on the house (46%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Durango'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 27,360 BTU/hr before the moisture allowance.

Other house sizes in Durango

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,100 BTU/hr; a 350 sq ft living room needs about 5,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,500 BTU/hr.

Month by month in Durango

Jul alone uses 51% of the year's cooling energy. The unit runs the equivalent of 183 hours a year at full output.

Durango against nearby cities

Of 53 Colorado cities here, Durango has the 48th highest cooling load. The range runs from Boulder at 15,700 BTU/hr to Grand Junction at 36,500.

Where Durango's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Durango La Plata County Airport, 10.5 miles from the center of Durango at 6,629 ft above sea level. That is close enough that the station's summers are Durango's summers.

No other city in this set uses Durango La Plata County Airport, so this sizing is Durango's alone.

The sun over Durango in late July

At 37.26°N, the noon sun on 21 July stands 73.1° above the horizon over Durango and the day runs 14 h 11 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. Shorter days give the house a longer night to shed the day's heat.

19,811 people live in Durango, the 34th largest of the 53 Colorado cities sized on this site. Coordinates used: 37.2645, -107.8741.

Durango AC sizing questions