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

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

3 tons central AC or heat pump, about 33,400 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 26% 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 718 square feet in this climate. For a single room, size by the room: 16.7 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Sterling (1 mi away). Jul is the hottest month, averaging a high of 91.2°F and a low of 62.2°F, with about 56 days a year at 90°F or more. That gives a design temperature of 97°F against 75°F inside.

What it costs to run

About 1,309 kWh a year at SEER2 14.3, or roughly $220 at Colorado's average residential rate of 16.8¢ per kWh. Cooling runs 4 months of the year here.

What drives the load in Sterling

Of the 33,400 BTU/hr, 15,840 comes through walls, roof and windows on a 97°F afternoon (47%), 13,000 is sun on the house (39%), 2,120 is four people and their appliances, and 2,500 is moisture the coil has to wring out of Sterling'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 30,960 BTU/hr before the moisture allowance.

Other house sizes in Sterling

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,500 BTU/hr; a 350 sq ft living room needs about 5,800 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 10,000 BTU/hr.

Month by month in Sterling

Jul alone uses 36% of the year's cooling energy. The unit runs the equivalent of 560 hours a year at full output.

Sterling against nearby cities

Of 53 Colorado cities here, Sterling has the 6th highest cooling load. The range runs from Boulder at 15,700 BTU/hr to Grand Junction at 36,500.

Where Sterling's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Sterling, 1 miles from the center of Sterling at 3,974 ft above sea level. That is close enough that the station's summers are Sterling's summers.

No other city in this set uses Sterling, so this sizing is Sterling's alone.

The sun over Sterling in late July

At 40.62°N, the noon sun on 21 July stands 69.8° above the horizon over Sterling and the day runs 14 h 29 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.

13,114 people live in Sterling, the 47th largest of the 53 Colorado cities sized on this site. Coordinates used: 40.6205, -103.1926.

Sterling AC sizing questions