The HVAC Sizing Mistake That Costs You for 15 Years

Bigger is not better. Here's why most homes get an oversized system — and how to push back.

Walk into ten HVAC quotes and nine of them will be sized using a rule of thumb: one ton of cooling per 500 square feet. It's wrong, and it's been wrong since the 1980s.

An oversized system cools the air quickly but doesn't run long enough to pull humidity out. You get a cold, clammy house, short cycling that wears out the compressor, and a 15-year repair bill that costs more than the unit did.

The fix is called a Manual J load calculation. It accounts for your insulation, windows, orientation, and air sealing. A contractor who refuses to do one — or who pretends they 'did one in their head' — is telling you something important.