Yes, and we do it with a load calculation rather than a square-footage rule of thumb. Sizing is the single most consequential decision in an air conditioning project, and in this region the most common error is going too big.

Why Square Footage Is Not Enough

The old rule — a ton of cooling per so many square feet — ignores almost everything that determines how much heat actually enters your house.

Two homes with identical footprints can have very different loads depending on insulation levels, window area and orientation, ceiling height, shading, air leakage, and construction type. A 1920s limestone house and a 2015 build are not remotely comparable, and Hill Country housing stock spans both.

West-facing glass matters enormously here. So does whether your ducts run through an unconditioned attic that reaches 140 degrees in August.

What a Load Calculation Actually Measures

We work through the building: square footage and volume, insulation R-values in walls and attic, window area with orientation and glazing type, exterior shading, air infiltration, occupancy, and internal heat sources.

The result is a number in BTUs representing the heat your home actually gains on a design day — the hottest conditions the system needs to handle, not the hottest imaginable.

That last distinction matters. Sizing for an extreme outlier rather than the design condition is one of the ways systems end up oversized.

Why Oversizing Is the Bigger Problem

Homeowners instinctively worry about a system being too small. In practice, oversizing causes more complaints.

An oversized air conditioner cools the house quickly, satisfies the thermostat, and shuts off. Those short cycles never run long enough to remove humidity — and roughly a third of what an air conditioner accomplishes on a humid Texas day is dehumidification.

The result is a house that reaches 73 degrees and still feels clammy. Occupants respond by lowering the thermostat further, which costs more and does not fix the actual problem.

Short cycling is also hard on compressors, produces uneven temperatures between rooms because the air never fully mixes, and costs more to buy in the first place.

The Right Size Runs Longer

A correctly sized system runs for extended periods on hot days. Homeowners sometimes read that as the system struggling.

It is the opposite. Long run times at steady output are what hold temperature within a narrow band and pull moisture out of the air. Variable-speed equipment takes this further, modulating output to match demand rather than cycling.

Dry air at 76 degrees is more comfortable than humid air at 73, and it costs less to produce.

Ductwork Constrains the Answer

Sizing the equipment is only half the calculation. The duct system has to be able to deliver the air.

Undersized returns force the blower against static pressure it was not designed for. Leaking supply ducts deliver conditioned air into your attic rather than your bedroom. Higher-end variable-speed equipment is more sensitive to these problems, not less.

We measure static pressure and inspect the ductwork as part of the assessment. Sometimes the honest recommendation is duct sealing plus mid-tier equipment rather than a premium system on compromised ducts.

When the Existing Size Is Wrong

Matching the tonnage of what is already installed is the most common shortcut in this industry, and it perpetuates whatever mistake was made originally.

If our calculation differs from what you have, we explain why. Homes change — added insulation, replaced windows, an addition — and the original sizing may no longer reflect the building.

Problem Rooms Are a Separate Question

If one room has never been comfortable, that is usually a distribution problem rather than a capacity problem, and a bigger system will not fix it. A ductless mini split often solves it directly for less than rebalancing the whole house.

For air conditioner installation or replacement, contact 72 Degrees or call (830) 468-5316. Financing is available.