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

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

4 tons central AC or heat pump, about 47,700 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 503 square feet in this climate. For a single room, size by the room: 23.9 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Harlingen Rio Grande Vly International (16.8 mi away). Aug is the hottest month, averaging a high of 97.2°F and a low of 75.3°F, with about 163 days a year at 90°F or more. That gives a design temperature of 105°F against 75°F inside.

What it costs to run

About 6,629 kWh a year at SEER2 14.3, or roughly $1,063 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 12 months of the year here.

What drives the load in Mercedes

Of the 47,700 BTU/hr, 21,600 comes through walls, roof and windows on a 105°F afternoon (45%), 13,000 is sun on the house (27%), 2,120 is four people and their appliances, and 11,000 is moisture the coil has to wring out of Mercedes'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 36,720 BTU/hr before the moisture allowance.

Other house sizes in Mercedes

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,600 BTU/hr; a 350 sq ft living room needs about 8,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 14,300 BTU/hr.

Month by month in Mercedes

Aug alone uses 16% of the year's cooling energy. The unit runs the equivalent of 1,986 hours a year at full output.

Mercedes against nearby cities

Of 252 Texas cities here, Mercedes has the 55th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Mercedes's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Harlingen Rio Grande Vly International, 16.8 miles from the center of Mercedes at 31 ft above sea level. That is close enough that the station's summers are Mercedes's summers.

2 other cities use the same station and get the same climate inputs. The closest to Mercedes: Harlingen (14 mi away, 3.7 mi from the station), San Benito (17 mi away, 7 mi from the station). Mercedes is farther from the station than 2 of them.

The sun over Mercedes in late July

At 26.15°N, the noon sun on 21 July stands 84.2° above the horizon over Mercedes and the day runs 13 h 24 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.

17,535 people live in Mercedes, the 170th largest of the 252 Texas cities sized on this site. Coordinates used: 26.1538, -97.9129.

Mercedes AC sizing questions