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

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

3.5 tons central AC or heat pump, about 39,500 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 607 square feet in this climate. For a single room, size by the room: 19.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Tahlequah (2 mi away). Jul is the hottest month, averaging a high of 93°F and a low of 69.1°F, with about 52 days a year at 90°F or more. That gives a design temperature of 99°F against 75°F inside.

What it costs to run

About 2,746 kWh a year at SEER2 14.3, or roughly $379 at Oklahoma's average residential rate of 13.81¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Tahlequah

Of the 39,500 BTU/hr, 17,280 comes through walls, roof and windows on a 99°F afternoon (44%), 13,000 is sun on the house (33%), 2,120 is four people and their appliances, and 7,100 is moisture the coil has to wring out of Tahlequah's summer air (18%).

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 32,400 BTU/hr before the moisture allowance.

Other house sizes in Tahlequah

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 6,900 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,900 BTU/hr.

Month by month in Tahlequah

Jul alone uses 27% of the year's cooling energy. The unit runs the equivalent of 993 hours a year at full output.

Tahlequah against nearby cities

Of 45 Oklahoma cities here, Tahlequah has the 42nd highest cooling load. The range runs from Miami at 35,600 BTU/hr to Ardmore at 44,900.

Where Tahlequah's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Tahlequah, 2 miles from the center of Tahlequah at 850 ft above sea level. That is close enough that the station's summers are Tahlequah's summers.

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

The sun over Tahlequah in late July

At 35.91°N, the noon sun on 21 July stands 74.5° above the horizon over Tahlequah and the day runs 14 h 05 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.

17,319 people live in Tahlequah, the 31st largest of the 45 Oklahoma cities sized on this site. Coordinates used: 35.9105, -94.9777.

Tahlequah AC sizing questions