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

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

3.5 tons central AC or heat pump, about 37,300 BTU/hr of load

Here the 20 BTU per square foot chart lands close: 3.5 tons against a load of 3.1 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 644 square feet in this climate. For a single room, size by the room: 18.6 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Dumas (0.9 mi away). Jul is the hottest month, averaging a high of 92.2°F and a low of 65.1°F, with about 73 days a year at 90°F or more. That gives a design temperature of 99°F against 75°F inside.

What it costs to run

About 1,984 kWh a year at SEER2 14.3, or roughly $318 at Texas's average residential rate of 16.03¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Dumas

Of the 37,300 BTU/hr, 17,280 comes through walls, roof and windows on a 99°F afternoon (46%), 13,000 is sun on the house (35%), 2,120 is four people and their appliances, and 4,900 is moisture the coil has to wring out of Dumas's summer air (13%).

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 32,400 BTU/hr before the moisture allowance.

Other house sizes in Dumas

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,800 BTU/hr; a 350 sq ft living room needs about 6,500 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,200 BTU/hr.

Month by month in Dumas

Jul alone uses 30% of the year's cooling energy. The unit runs the equivalent of 761 hours a year at full output.

Dumas against nearby cities

Of 252 Texas cities here, Dumas has the 251st highest cooling load. The range runs from Levelland at 37,300 BTU/hr to Laredo at 51,500.

Where Dumas's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Dumas, 0.9 miles from the center of Dumas at 3,655 ft above sea level. That is close enough that the station's summers are Dumas's summers.

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

The sun over Dumas in late July

At 35.86°N, the noon sun on 21 July stands 74.5° above the horizon over Dumas and the day runs 14 h 05 min from sunrise to sunset. A lower noon sun puts more of the day's heat on east and west walls than on the roof, which is why shading west glass pays off here. Shorter days give the house a longer night to shed the day's heat.

14,834 people live in Dumas, the 198th largest of the 252 Texas cities sized on this site. Coordinates used: 35.8620, -101.9650.

Dumas AC sizing questions