What size AC for Bay City, TX? 3.5 tons for 2,000 sq ft

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

3.5 tons central AC or heat pump, about 41,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.4 tons. This is one of the climates the chart was written for.

If a contractor quotes you more than 3.5 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 583 square feet in this climate. For a single room, size by the room: 20.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Bay City Wtr Wks (1 mi away). Aug is the hottest month, averaging a high of 91.4°F and a low of 72.8°F, with about 88 days a year at 90°F or more. That gives a design temperature of 98°F against 75°F inside.

What it costs to run

About 4,294 kWh a year at SEER2 14.3, or roughly $688 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 9 months of the year here.

What drives the load in Bay City

Of the 41,200 BTU/hr, 16,560 comes through walls, roof and windows on a 98°F afternoon (40%), 13,000 is sun on the house (32%), 2,120 is four people and their appliances, and 9,500 is moisture the coil has to wring out of Bay City'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 31,680 BTU/hr before the moisture allowance.

Other house sizes in Bay City

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,100 BTU/hr; a 350 sq ft living room needs about 7,200 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,400 BTU/hr.

Month by month in Bay City

Aug alone uses 19% of the year's cooling energy. The unit runs the equivalent of 1,491 hours a year at full output.

Bay City against nearby cities

Of 252 Texas cities here, Bay City has the 241st highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Bay City's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Bay City Wtr Wks, 1 miles from the center of Bay City at 52 ft above sea level. That is close enough that the station's summers are Bay City's summers.

No other city in this set uses Bay City Wtr Wks, so this sizing is Bay City's alone.

The sun over Bay City in late July

At 28.98°N, the noon sun on 21 July stands 81.4° above the horizon over Bay City and the day runs 13 h 35 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.

17,471 people live in Bay City, the 171st largest of the 252 Texas cities sized on this site. Coordinates used: 28.9835, -95.9599.

Bay City AC sizing questions