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

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

2.5 tons central AC or heat pump, about 26,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 60% 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 916 square feet in this climate. For a single room, size by the room: 13.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Monument 3s (1.8 mi away). Jul is the hottest month, averaging a high of 84.1°F and a low of 52.7°F, with about 15 days a year at 90°F or more. That gives a design temperature of 89°F against 75°F inside.

What it costs to run

About 355 kWh a year at SEER2 14.3, or roughly $60 at Colorado's average residential rate of 16.8¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Monument

Of the 26,200 BTU/hr, 10,080 comes through walls, roof and windows on a 89°F afternoon (38%), 13,000 is sun on the house (50%), 2,120 is four people and their appliances, and 1,000 is moisture the coil has to wring out of Monument'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 25,200 BTU/hr before the moisture allowance.

Other house sizes in Monument

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,000 BTU/hr; a 350 sq ft living room needs about 4,600 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 7,900 BTU/hr.

Month by month in Monument

Jul alone uses 43% of the year's cooling energy. The unit runs the equivalent of 194 hours a year at full output.

Monument against nearby cities

Of 53 Colorado cities here, Monument has the 51st highest cooling load. The range runs from Boulder at 15,700 BTU/hr to Grand Junction at 36,500.

Where Monument's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Monument 3s, 1.8 miles from the center of Monument at 6,821 ft above sea level. That is close enough that the station's summers are Monument's summers.

No other city in this set uses Monument 3s, so this sizing is Monument's alone.

The sun over Monument in late July

At 39.07°N, the noon sun on 21 July stands 71.3° above the horizon over Monument 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.

13,408 people live in Monument, the 46th largest of the 53 Colorado cities sized on this site. Coordinates used: 39.0744, -104.8442.

Monument AC sizing questions