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

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

2.5 tons central AC or heat pump, about 29,200 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 44% 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 822 square feet in this climate. For a single room, size by the room: 14.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Riverton (5.6 mi away). Jul is the hottest month, averaging a high of 88.1°F and a low of 55.7°F, with about 31 days a year at 90°F or more. That gives a design temperature of 93°F against 75°F inside.

What it costs to run

About 627 kWh a year at SEER2 14.3, or roughly $88 at Wyoming's average residential rate of 14.01¢ per kWh. Cooling runs 3 months of the year here.

What drives the load in Riverton

Of the 29,200 BTU/hr, 12,960 comes through walls, roof and windows on a 93°F afternoon (44%), 13,000 is sun on the house (45%), 2,120 is four people and their appliances, and 1,100 is moisture the coil has to wring out of Riverton'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 28,080 BTU/hr before the moisture allowance.

Other house sizes in Riverton

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,200 BTU/hr; a 350 sq ft living room needs about 5,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 8,800 BTU/hr.

Month by month in Riverton

Jul alone uses 45% of the year's cooling energy. The unit runs the equivalent of 307 hours a year at full output.

Riverton against nearby cities

Of 11 Wyoming cities here, Riverton has the 3rd highest cooling load. The range runs from Jackson at 21,700 BTU/hr to Casper at 30,000.

Where Riverton's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Riverton, 5.6 miles from the center of Riverton at 5,633 ft above sea level. That is close enough that the station's summers are Riverton's summers.

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

The sun over Riverton in late July

At 43.03°N, the noon sun on 21 July stands 67.4° above the horizon over Riverton and the day runs 14 h 42 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.

10,953 people live in Riverton, the 9th largest of the 11 Wyoming cities sized on this site. Coordinates used: 43.0263, -108.3813.

Riverton AC sizing questions