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

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

4 tons central AC or heat pump, about 49,600 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 484 square feet in this climate. For a single room, size by the room: 24.8 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Rio Grande City (12.2 mi away). Aug is the hottest month, averaging a high of 99.4°F and a low of 75.1°F, with about 187 days a year at 90°F or more. That gives a design temperature of 107°F against 75°F inside.

What it costs to run

About 6,648 kWh a year at SEER2 14.3, or roughly $1,066 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 11 months of the year here.

What drives the load in Roma

Of the 49,600 BTU/hr, 23,040 comes through walls, roof and windows on a 107°F afternoon (46%), 13,000 is sun on the house (26%), 2,120 is four people and their appliances, and 11,400 is moisture the coil has to wring out of Roma'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 38,160 BTU/hr before the moisture allowance.

Other house sizes in Roma

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,700 BTU/hr; a 350 sq ft living room needs about 8,700 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 14,900 BTU/hr.

Month by month in Roma

Aug alone uses 16% of the year's cooling energy. The unit runs the equivalent of 1,916 hours a year at full output.

Roma against nearby cities

Of 252 Texas cities here, Roma has the 16th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Roma's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Rio Grande City, 12.2 miles from the center of Roma at 172 ft above sea level. That is close enough that the station's summers are Roma's summers.

1 other city uses the same station and get the same climate inputs. The closest to Roma: Rio Grande City (12 mi away, 0.7 mi from the station). Roma is farther from the station than 1 of them.

The sun over Roma in late July

At 26.41°N, the noon sun on 21 July stands 84.0° above the horizon over Roma and the day runs 13 h 25 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.

11,635 people live in Roma, the 224th largest of the 252 Texas cities sized on this site. Coordinates used: 26.4147, -99.0039.

Roma AC sizing questions