What size AC for Guymon, OK? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 39,700 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.3 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 604 square feet in this climate. For a single room, size by the room: 19.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Guymon Municipal Airport (1.7 mi away). Jul is the hottest month, averaging a high of 95°F and a low of 66.5°F, with about 89 days a year at 90°F or more. That gives a design temperature of 102°F against 75°F inside.

What it costs to run

About 2,279 kWh a year at SEER2 14.3, or roughly $315 at Oklahoma's average residential rate of 13.81¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Guymon

Of the 39,700 BTU/hr, 19,440 comes through walls, roof and windows on a 102°F afternoon (49%), 13,000 is sun on the house (33%), 2,120 is four people and their appliances, and 5,200 is moisture the coil has to wring out of Guymon's summer air (13%).

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 34,560 BTU/hr before the moisture allowance.

Other house sizes in Guymon

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,000 BTU/hr; a 350 sq ft living room needs about 7,000 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,900 BTU/hr.

Month by month in Guymon

Jul alone uses 30% of the year's cooling energy. The unit runs the equivalent of 820 hours a year at full output.

Guymon against nearby cities

Of 45 Oklahoma cities here, Guymon has the 38th highest cooling load. The range runs from Miami at 35,600 BTU/hr to Ardmore at 44,900.

Where Guymon's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Guymon Municipal Airport, 1.7 miles from the center of Guymon at 3,113 ft above sea level. That is close enough that the station's summers are Guymon's summers.

No other city in this set uses Guymon Municipal Airport, so this sizing is Guymon's alone.

The sun over Guymon in late July

At 36.69°N, the noon sun on 21 July stands 73.7° above the horizon over Guymon and the day runs 14 h 09 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.

12,397 people live in Guymon, the 37th largest of the 45 Oklahoma cities sized on this site. Coordinates used: 36.6901, -101.4770.

Guymon AC sizing questions