What size AC for McAlester, OK? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 43,100 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.6 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 4 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 557 square feet in this climate. For a single room, size by the room: 21.5 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Mcalester Regional Airport (3 mi away). Jul is the hottest month, averaging a high of 93.2°F and a low of 72°F, with about 73 days a year at 90°F or more. That gives a design temperature of 100°F against 75°F inside.

What it costs to run

About 3,351 kWh a year at SEER2 14.3, or roughly $463 at Oklahoma's average residential rate of 13.81¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in McAlester

Of the 43,100 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (42%), 13,000 is sun on the house (30%), 2,120 is four people and their appliances, and 9,900 is moisture the coil has to wring out of McAlester's summer air (23%).

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 33,120 BTU/hr before the moisture allowance.

Other house sizes in McAlester

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,900 BTU/hr.

Month by month in McAlester

Jul alone uses 26% of the year's cooling energy. The unit runs the equivalent of 1,113 hours a year at full output.

McAlester against nearby cities

Of 45 Oklahoma cities here, McAlester has the 19th highest cooling load. The range runs from Miami at 35,600 BTU/hr to Ardmore at 44,900.

Where McAlester's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Mcalester Regional Airport, 3 miles from the center of McAlester at 753 ft above sea level. That is close enough that the station's summers are McAlester's summers.

No other city in this set uses Mcalester Regional Airport, so this sizing is McAlester's alone.

The sun over McAlester in late July

At 34.93°N, the noon sun on 21 July stands 75.5° above the horizon over McAlester and the day runs 14 h 00 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.

18,108 people live in McAlester, the 30th largest of the 45 Oklahoma cities sized on this site. Coordinates used: 34.9261, -95.7736.

McAlester AC sizing questions