What size AC for San Antonio, TX? 4 tons for 2,000 sq ft

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

4 tons central AC or heat pump, about 46,800 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, which falls short here. On a design day the unit runs flat out and the house still drifts above 75°F by late afternoon.

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 513 square feet in this climate. For a single room, size by the room: 23.4 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at San Antonio International Airport (6.1 mi away). Aug is the hottest month, averaging a high of 96°F and a low of 74.9°F, with about 122 days a year at 90°F or more. That gives a design temperature of 104°F against 75°F inside.

What it costs to run

About 4,945 kWh a year at SEER2 14.3, or roughly $793 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in San Antonio

Of the 46,800 BTU/hr, 20,880 comes through walls, roof and windows on a 104°F afternoon (45%), 13,000 is sun on the house (28%), 2,120 is four people and their appliances, and 10,800 is moisture the coil has to wring out of San Antonio'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 36,000 BTU/hr before the moisture allowance.

Other house sizes in San Antonio

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,500 BTU/hr; a 350 sq ft living room needs about 8,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 14,000 BTU/hr.

Month by month in San Antonio

Aug alone uses 20% of the year's cooling energy. The unit runs the equivalent of 1,511 hours a year at full output.

San Antonio against nearby cities

Of 252 Texas cities here, San Antonio has the 70th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where San Antonio's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is San Antonio International Airport, 6.1 miles from the center of San Antonio at 799 ft above sea level. That is close enough that the station's summers are San Antonio's summers.

2 other cities use the same station and get the same climate inputs. The closest to San Antonio: Helotes (12 mi away, 12 mi from the station), Fair Oaks Ranch (21 mi away, 16.7 mi from the station). San Antonio sits closer to the station than any of them, so its numbers are the best measured of the group.

The sun over San Antonio in late July

At 29.46°N, the noon sun on 21 July stands 80.9° above the horizon over San Antonio and the day runs 13 h 37 min from sunrise to sunset. With the sun that close to overhead, the roof takes most of the heat at midday and the west wall takes the rest after 3 pm. Shorter days give the house a longer night to shed the day's heat.

1,526,656 people live in San Antonio, the 2nd largest of the 252 Texas cities sized on this site. Coordinates used: 29.4628, -98.5246.

San Antonio AC sizing questions