What size AC for Green River, WY? 2.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Green River 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 Green River (0.3 mi away). Jul is the hottest month, averaging a high of 86.6°F and a low of 52.9°F, with about 30 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 439 kWh a year at SEER2 14.3, or roughly $62 at Wyoming's average residential rate of 14.01¢ per kWh. Cooling runs 2 months of the year here.

What drives the load in Green River

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 Green River'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 Green River

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 Green River

Jul alone uses 49% of the year's cooling energy. The unit runs the equivalent of 221 hours a year at full output.

Green River against nearby cities

Of 11 Wyoming cities here, Green River has the 5th highest cooling load. The range runs from Jackson at 21,700 BTU/hr to Casper at 30,000.

Where Green River's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Green River, 0.3 miles from the center of Green River at 6,160 ft above sea level. That is close enough that the station's summers are Green River's summers.

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

The sun over Green River in late July

At 41.51°N, the noon sun on 21 July stands 68.9° above the horizon over Green River and the day runs 14 h 34 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. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

11,474 people live in Green River, the 8th largest of the 11 Wyoming cities sized on this site. Coordinates used: 41.5129, -109.4708.

Green River AC sizing questions