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

What size AC a 2,000 sq ft house in Helotes 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 (12 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 Helotes

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 Helotes'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 Helotes

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 Helotes

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

Helotes against nearby cities

Of 252 Texas cities here, Helotes has the 114th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Helotes's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is San Antonio International Airport, 12 miles from the center of Helotes at 799 ft above sea level. That is close enough that the station's summers are Helotes's summers.

2 other cities use the same station and get the same climate inputs. The closest to Helotes: Fair Oaks Ranch (12 mi away, 16.7 mi from the station), San Antonio (12 mi away, 6.1 mi from the station). Helotes is farther from the station than 1 of them.

The sun over Helotes in late July

At 29.58°N, the noon sun on 21 July stands 80.8° above the horizon over Helotes 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.

10,223 people live in Helotes, the 245th largest of the 252 Texas cities sized on this site. Coordinates used: 29.5780, -98.6805.

Helotes AC sizing questions