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

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

4 tons central AC or heat pump, about 44,000 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.7 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 546 square feet in this climate. For a single room, size by the room: 22 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Houston William P Hobby Airport (11.6 mi away). Aug is the hottest month, averaging a high of 93.5°F and a low of 76.7°F, with about 101 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 5,282 kWh a year at SEER2 14.3, or roughly $847 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Houston

Of the 44,000 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (43%), 13,000 is sun on the house (30%), 2,120 is four people and their appliances, and 10,200 is moisture the coil has to wring out of Houston'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 33,840 BTU/hr before the moisture allowance.

Other house sizes in Houston

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,300 BTU/hr; a 350 sq ft living room needs about 7,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 13,200 BTU/hr.

Month by month in Houston

Aug alone uses 19% of the year's cooling energy. The unit runs the equivalent of 1,717 hours a year at full output.

Houston against nearby cities

Of 252 Texas cities here, Houston has the 178th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Houston's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Houston William P Hobby Airport, 11.6 miles from the center of Houston at 43 ft above sea level. That is close enough that the station's summers are Houston's summers.

8 other cities use the same station and get the same climate inputs. The closest to Houston: West University Place (5 mi away, 10.2 mi from the station), Bellaire (7 mi away, 11.5 mi from the station), Galena Park (10 mi away, 7.4 mi from the station), South Houston (13 mi away, 3.4 mi from the station), Pasadena (17 mi away, 7.9 mi from the station). Houston is farther from the station than 6 of them.

The sun over Houston in late July

At 29.79°N, the noon sun on 21 July stands 80.6° above the horizon over Houston and the day runs 13 h 38 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.

2,390,125 people live in Houston, the largest of the 252 Texas cities sized on this site. Coordinates used: 29.7857, -95.3888.

Houston AC sizing questions