How Often Should You Change an AC Filter in Florida?

What changes the interval

• Filter thickness: one-inch filters load fast; four- and five-inch media filters can last several months.
• Pets, especially shedding breeds, dramatically shorten filter life.
• Spring oak and pine pollen, which is heavy in most Tallahassee neighborhoods.
• Construction or renovation dust anywhere in the home.
• Runtime — a system running 12 hours a day loads a filter faster than one running four.

Choosing a filter without hurting airflow

Higher MERV ratings capture smaller particles but create more resistance. On a system with marginal ductwork, a very restrictive filter can reduce airflow enough to cause weak cooling or coil freezing.

A moderate MERV filter changed on schedule usually outperforms a high-MERV filter left in too long. If someone in the home has significant allergy needs, a thicker media cabinet is a better solution than a restrictive one-inch filter.

How to check instead of guessing

Hold the filter up to a light. If light passes through easily, it has life left. If the surface is grey and matted, replace it regardless of the date.

Write the install date on the filter frame with a marker — it removes the guesswork entirely.

What a neglected filter causes

• Reduced airflow and lower cooling capacity.
• Frozen evaporator coil.
• Dust accumulating on the coil and blower wheel, which requires cleaning to correct.
• Longer run times and higher energy use.
• Extra strain on the blower motor.

Getting the size right

Filter size is printed on the frame. Buying the wrong size and forcing it in leaves gaps that let unfiltered air bypass, which puts dust directly on the coil.