What size AC for Grand Junction, CO? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 36,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 15% 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 3.5 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 657 square feet in this climate. For a single room, size by the room: 18.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Grand Junction Walker Field (3.4 mi away). Jul is the hottest month, averaging a high of 94.5°F and a low of 63.9°F, with about 68 days a year at 90°F or more. That gives a design temperature of 101°F against 75°F inside.

What it costs to run

About 1,609 kWh a year at SEER2 14.3, or roughly $270 at Colorado's average residential rate of 16.8¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Grand Junction

Of the 36,500 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (51%), 13,000 is sun on the house (36%), 2,120 is four people and their appliances, and 2,700 is moisture the coil has to wring out of Grand Junction'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 33,840 BTU/hr before the moisture allowance.

Other house sizes in Grand Junction

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,700 BTU/hr; a 350 sq ft living room needs about 6,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,000 BTU/hr.

Month by month in Grand Junction

Jul alone uses 36% of the year's cooling energy. The unit runs the equivalent of 630 hours a year at full output.

Grand Junction against nearby cities

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

Where Grand Junction's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Grand Junction Walker Field, 3.4 miles from the center of Grand Junction at 4,824 ft above sea level. That is close enough that the station's summers are Grand Junction's summers.

1 other city uses the same station and get the same climate inputs. The closest to Grand Junction: Fruita (10 mi away, 10.2 mi from the station). Grand Junction sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Grand Junction in late July

At 39.09°N, the noon sun on 21 July stands 71.3° above the horizon over Grand Junction and the day runs 14 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. Shorter days give the house a longer night to shed the day's heat.

70,554 people live in Grand Junction, the 17th largest of the 53 Colorado cities sized on this site. Coordinates used: 39.0891, -108.5675.

Grand Junction AC sizing questions