How to Choose the Right Size HVAC System for Your Texas Home

If your AC is constantly running but never cooling your house properly, or if it cycles on and off every few minutes, there’s a good chance your system is the wrong size. In Texas, where summers regularly push past 100°F, getting the right HVAC size isn’t optional — it’s the difference between comfort and misery, and between reasonable energy bills and shocking ones.

This guide walks you through exactly how to size an HVAC system for a Texas home, without the guesswork.

Why Size Matters More in Texas Than Anywhere Else

Texas heat is intense and long. Houston and San Antonio deal with extreme humidity on top of the heat. Dallas and Austin get brutal dry heat with intense sun exposure. An undersized system runs nonstop and still can’t keep up. An oversized system cools too fast, shuts off before removing humidity, and causes short cycling — which wears out the compressor early.

The goal is a system that runs in longer, steady cycles and maintains both temperature and humidity control.

The Standard Rule: 400 Square Feet Per Ton

The most commonly used starting point for Texas residential HVAC sizing is approximately 400 square feet per ton of cooling capacity. This accounts for the Texas climate being more demanding than the national average.

Important: These are starting estimates. Several factors adjust the final recommendation.

Factors That Change Your Tonnage Calculation

Insulation quality — A well-insulated home in Austin needs less tonnage than a poorly insulated one the same size. If your attic insulation is thin or old, add half a ton to your estimate.

Sun exposure — A west-facing home in San Antonio takes significantly more solar heat load than one facing north. Homes with large windows facing south or west may need more capacity.

Ceiling height — Standard calculations assume 8-foot ceilings. If your home has 10 or 12-foot ceilings, add cooling capacity proportionally.

Ductwork condition — Leaky or poorly insulated ducts in a hot Texas attic can reduce system efficiency by 20–30%. Fix ductwork before upsizing equipment.

Number of occupants — Every person in the home adds heat. A 2,000 sq ft home with 6 people needs more capacity than one with 2 people.

SEER2 Rating: Efficiency in the Texas Heat

Since January 2023, all HVAC systems sold in Texas must meet the SEER2 standard (Seasonal Energy Efficiency Ratio 2). The minimum for Texas is 14.3 SEER2 for air conditioners and 14.3 SEER2 / 8.1 HSPF2 for heat pumps.

Higher SEER2 means lower monthly electricity bills. In Texas, where the AC runs 8–9 months per year, a 16 SEER2 system vs a 14.3 SEER2 system can mean hundreds of dollars in annual savings.

Gas System or Electric System?

Texas homes use both, depending on location and existing infrastructure.

Gas split systems (condenser + air handler + gas furnace) are common in Dallas, San Antonio, and parts of Austin where natural gas lines are available. They heat faster and are typically more cost-effective for heating in winter.

Electric systems (condenser + air handler + electric heat kit) work well where gas isn’t available or where a homeowner prefers all-electric. In mild Texas winters, the heating demand is low enough that electric heat kits perform well.

Heat pumps provide both heating and cooling from a single system and are increasingly popular for Texas homes that want efficiency year-round.

Get Your System Right the First Time

At Xpress Supply, we carry complete HVAC systems in stock at our Texas warehouses — Goodman, Rheem, Carrier, and more — in every tonnage from 1.5 to 5 tons. Same-day pickup is available in Houston and San Antonio, and we ship across Texas in under 72 hours.

If you’re not sure what size you need, call us at (855) 533-0222 or use our HVAC System Finder to get a recommendation in minutes.

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