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

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

3.5 tons central AC or heat pump, about 40,400 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 594 square feet in this climate. For a single room, size by the room: 20.2 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at El Reno 1 N (0.6 mi away). Jul is the hottest month, averaging a high of 93.5°F and a low of 70.1°F, with about 75 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 2,674 kWh a year at SEER2 14.3, or roughly $369 at Oklahoma's average residential rate of 13.81¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in El Reno

Of the 40,400 BTU/hr, 18,000 comes through walls, roof and windows on a 100°F afternoon (45%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 7,300 is moisture the coil has to wring out of El Reno'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 33,120 BTU/hr before the moisture allowance.

Other house sizes in El Reno

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 7,100 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,100 BTU/hr.

Month by month in El Reno

Jul alone uses 29% of the year's cooling energy. The unit runs the equivalent of 946 hours a year at full output.

El Reno against nearby cities

Of 45 Oklahoma cities here, El Reno has the 34th highest cooling load. The range runs from Miami at 35,600 BTU/hr to Ardmore at 44,900.

Where El Reno's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is El Reno 1 N, 0.6 miles from the center of El Reno at 1,325 ft above sea level. That is close enough that the station's summers are El Reno's summers.

No other city in this set uses El Reno 1 N, so this sizing is El Reno's alone.

The sun over El Reno in late July

At 35.54°N, the noon sun on 21 July stands 74.9° above the horizon over El Reno 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.

20,041 people live in El Reno, the 28th largest of the 45 Oklahoma cities sized on this site. Coordinates used: 35.5418, -97.9613.

El Reno AC sizing questions