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

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

3.5 tons central AC or heat pump, about 41,300 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.4 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 581 square feet in this climate. For a single room, size by the room: 20.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Clinton-Sherman Airport (12.9 mi away). Jul is the hottest month, averaging a high of 94.2°F and a low of 71.3°F, with about 90 days a year at 90°F or more. That gives a design temperature of 101°F against 75°F inside.

What it costs to run

About 2,921 kWh a year at SEER2 14.3, or roughly $403 at Oklahoma's average residential rate of 13.81¢ per kWh. Cooling runs 6 months of the year here.

What drives the load in Elk City

Of the 41,300 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (45%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 7,400 is moisture the coil has to wring out of Elk City'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 33,840 BTU/hr before the moisture allowance.

Other house sizes in Elk City

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,100 BTU/hr; a 350 sq ft living room needs about 7,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,400 BTU/hr.

Month by month in Elk City

Jul alone uses 28% of the year's cooling energy. The unit runs the equivalent of 1,012 hours a year at full output.

Elk City against nearby cities

Of 45 Oklahoma cities here, Elk City has the 24th highest cooling load. The range runs from Miami at 35,600 BTU/hr to Ardmore at 44,900.

Where Elk City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Clinton-Sherman Airport, 12.9 miles from the center of Elk City at 1,918 ft above sea level. That is close enough that the station's summers are Elk City's summers.

No other city in this set uses Clinton-Sherman Airport, so this sizing is Elk City's alone.

The sun over Elk City in late July

At 35.39°N, the noon sun on 21 July stands 75.0° above the horizon over Elk City and the day runs 14 h 03 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.

11,383 people live in Elk City, the 42nd largest of the 45 Oklahoma cities sized on this site. Coordinates used: 35.3896, -99.4287.

Elk City AC sizing questions