How often should you change your AC filter in Florida?

The light test

Forget the calendar for a second. Pull your filter out and hold it up to a light. If light passes through easily, it's fine. If you can barely see light through it, it's done — replace it now, regardless of what month it is.

This is the most honest test there is. A clogged filter makes your system work harder, cool worse, and run up your electric bill. Two minutes, no tools, no guessing.

The 1–3 month rhythm

As a baseline for South Florida homes: check monthly, expect to replace every one to three months. Where you land in that range depends on your house:

• Pets: One dog or cat moves you toward monthly. Multiple pets, definitely monthly.
• Dust and pollen: New construction nearby, unpaved surroundings, or high-pollen months shorten filter life.
• Run time: If your thermostat rarely rests from April through October, your filter is filtering constantly.
• Allergies or asthma in the house: Change on the early side. A loaded filter restricts airflow, and air can slip around it instead of through it.

A quick word on MERV

MERV is just the filtration score — higher number, smaller particles caught. MERV 8 handles dust and pollen and suits most homes. MERV 11 adds pet dander and mold spores. MERV 13 catches the fine stuff but restricts airflow more, which can strain an older system. When in doubt, match what was already in there, or check your unit's manual.

Buy by the numbers on the frame

The size printed on your filter's frame — something like 20x25x1 — is the nominal size: what the filter is sold as. The actual filter runs about a quarter to half inch smaller in each direction so it slides into the slot. That's normal. Always buy by the nominal size on the frame; that's what the shelf is organized by. If the label is faded or confusing, a photo of it is all you need — FilterJungle reads the size off the label for free, no account required.

Make it a habit, not a project

Pick a cue you'll actually follow: the first of the month, the day the electric bill arrives, whatever sticks. Check the filter, hold it to the light, done. Your home has a lot to remember — this is one small thing you can stop thinking about once the rhythm's set.