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

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

4 tons central AC or heat pump, about 42,200 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.5 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 569 square feet in this climate. For a single room, size by the room: 21.1 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Fredericksburg (2.7 mi away). Aug is the hottest month, averaging a high of 94.2°F and a low of 70.2°F, with about 104 days a year at 90°F or more. That gives a design temperature of 102°F against 75°F inside.

What it costs to run

About 3,511 kWh a year at SEER2 14.3, or roughly $563 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 7 months of the year here.

What drives the load in Fredericksburg

Of the 42,200 BTU/hr, 19,440 comes through walls, roof and windows on a 102°F afternoon (46%), 13,000 is sun on the house (31%), 2,120 is four people and their appliances, and 7,600 is moisture the coil has to wring out of Fredericksburg's summer air (18%).

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 34,560 BTU/hr before the moisture allowance.

Other house sizes in Fredericksburg

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 3,200 BTU/hr; a 350 sq ft living room needs about 7,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 12,700 BTU/hr.

Month by month in Fredericksburg

Aug alone uses 22% of the year's cooling energy. The unit runs the equivalent of 1,191 hours a year at full output.

Fredericksburg against nearby cities

Of 252 Texas cities here, Fredericksburg has the 228th highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Fredericksburg's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Fredericksburg, 2.7 miles from the center of Fredericksburg at 1,685 ft above sea level. That is close enough that the station's summers are Fredericksburg's summers.

No other city in this set uses Fredericksburg, so this sizing is Fredericksburg's alone.

The sun over Fredericksburg in late July

At 30.27°N, the noon sun on 21 July stands 80.1° above the horizon over Fredericksburg and the day runs 13 h 40 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.

11,766 people live in Fredericksburg, the 222nd largest of the 252 Texas cities sized on this site. Coordinates used: 30.2657, -98.8757.

Fredericksburg AC sizing questions