When you get replacement quotes, you'll hear numbers like "4-ton, 16 SEER2." Behind those two numbers lies most of what determines whether your new system delivers 15 comfortable years or 15 years of clammy rooms and high bills. Here's what they actually mean — and the sizing mistake half the industry still makes.
What a 'ton' actually is
A ton has nothing to do with weight — it's cooling power: 12,000 BTUs per hour, a unit dating back to the ice-harvesting era. Residential systems run from 1.5 to 5 tons. The rough Texas rule of thumb is one ton per 500–700 square feet, but that range is wide for a reason: a shaded 1970s home with new windows and a radiant barrier needs far less than a sun-blasted two-story with builder-grade glass.
Why bigger is genuinely worse
The most common sizing mistake isn't too small — it's too big. An oversized AC cools the air fast and then shuts off before it dehumidifies. In our humid climate, that produces the classic oversized-system feel: cold, damp, clammy rooms and short, hard-starting cycles that wear the equipment out early.
A properly sized system runs longer, gentler cycles that wring moisture out of the air. Counterintuitively, 75° at 45% humidity feels better than 72° at 60% — proper sizing literally lets you set the thermostat higher and feel cooler.
The right way: a real load calculation
Professional sizing uses a Manual J load calculation: square footage, ceiling heights, insulation levels, window area and orientation, duct location, and infiltration. It takes real measurement, which is why corner-cutting installers skip it and just match the old unit's size — faithfully copying whatever mistake the last installer made. When we quote a replacement, the load calc is part of the visit. If a quote arrives without anyone measuring anything, that tells you something.
SEER2, translated to dollars
SEER2 is the efficiency rating — how much cooling you get per dollar of electricity, tested under realistic duct pressures (that's the '2'). The federal minimum for Texas is 14.3 SEER2; premium systems reach 20+.
In a cooling-dominated climate like ours, stepping from an old 10-SEER system to a modern 15.2 SEER2 unit typically cuts cooling costs by roughly a third. Above 17 SEER2, buy for comfort features — variable-speed compressors, better humidity control, quieter operation — rather than pure payback, because the incremental savings flatten out.
The bottom line for Dallas homeowners
Insist on a load calculation, be suspicious of 'same size as before,' and put your upgrade dollars into right-sizing and duct quality before chasing maximum SEER2. A correctly sized 16 SEER2 system on healthy ducts will outperform an oversized 20 SEER2 showpiece every single Texas summer.
From the team at Strike Force HVAC
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