Placentia: how AC sizing actually works

We get the same question from Placentia homeowners getting replacement quotes: “the other guy said I need a 5-ton, the next guy said 3.5-ton, what’s right?” The honest answer is, neither of them did a real load calculation, and you should be cautious of both.

What a real load calculation includes

A Manual J calculation — the industry standard — looks at:

• Total square footage and ceiling height
• Window count, size, and orientation
• Insulation R-values for walls, ceiling, floor
• Building tightness and infiltration
• Local design temperatures
• Internal heat gains (people, appliances, lighting)

A real calculation in Placentia, where summer design temps are around 95-100, will land most 2,000 sq ft homes between 2.5 and 3.5 tons. Houses with poor insulation or lots of west-facing glass might push toward 4. Almost nothing in a typical Placentia tract home actually needs 5 tons.

Why you keep getting oversized quotes

A lot of installers size by square footage alone — usually 400-500 sq ft per ton — and round up “to be safe.” It’s quick, it leaves margin for error, and it usually leads to oversized systems that short-cycle, dehumidify poorly, and die early.

If you’re getting a replacement quote in Placentia, ask the installer if they did a Manual J. Ask for the worksheet. If they can’t produce one, get another quote. More on AC install and what we look at when sizing.