What size AC for Commerce City, CO? 3 tons for 2,000 sq ft

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

3 tons central AC or heat pump, about 31,900 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 32% 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 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 753 square feet in this climate. For a single room, size by the room: 15.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Denver International Airport (7.8 mi away). Jul is the hottest month, averaging a high of 89.9°F and a low of 60.2°F, with about 46 days a year at 90°F or more. That gives a design temperature of 95°F against 75°F inside.

What it costs to run

About 1,109 kWh a year at SEER2 14.3, or roughly $186 at Colorado's average residential rate of 16.8¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Commerce City

Of the 31,900 BTU/hr, 14,400 comes through walls, roof and windows on a 95°F afternoon (45%), 13,000 is sun on the house (41%), 2,120 is four people and their appliances, and 2,400 is moisture the coil has to wring out of Commerce City's summer air (8%).

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 29,520 BTU/hr before the moisture allowance.

Other house sizes in Commerce City

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,400 BTU/hr; a 350 sq ft living room needs about 5,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 9,500 BTU/hr.

Month by month in Commerce City

Jul alone uses 37% of the year's cooling energy. The unit runs the equivalent of 497 hours a year at full output.

Commerce City against nearby cities

Of 53 Colorado cities here, Commerce City has the 24th highest cooling load. The range runs from Boulder at 15,700 BTU/hr to Grand Junction at 36,500.

Where Commerce City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Denver International Airport, 7.8 miles from the center of Commerce City at 5,404 ft above sea level. That is close enough that the station's summers are Commerce City's summers.

1 other city uses the same station and get the same climate inputs. The closest to Commerce City: Brighton (6 mi away, 11 mi from the station). Commerce City sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over Commerce City in late July

At 39.88°N, the noon sun on 21 July stands 70.5° above the horizon over Commerce City and the day runs 14 h 25 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.

70,245 people live in Commerce City, the 18th largest of the 53 Colorado cities sized on this site. Coordinates used: 39.8828, -104.7949.

Commerce City AC sizing questions