Repair, replace, maintain
How often should I change my AC filter in Florida?
More often than the sleeve says. Florida systems run most of the year, and a Longwood lot under oak canopy loads a filter with pollen in spring and leaf dust in autumn. Check it monthly and change it when you can no longer see light through it.
Why the sleeve is wrong here
Runtime and canopy, not the calendar
The interval printed on a filter sleeve assumes a temperate climate and a system that rests for months at a time. Neither is true here: the nearest long-record station logs roughly 3,452 cooling degree days a year, so the blower is moving air through that filter for most of the calendar. A 90-day filter in a Florida house is not a 90-day filter.
Longwood adds canopy. Mature oak and pine across the city and the Wekiva-area subdivisions mean a spring pollen load and an autumn leaf-dust load that a filter in an open subdivision never sees. Households with pets or an attic air handler in a dusty attic should assume the shorter end of any interval.
What a blocked filter actually causes
Restricted airflow freezes coils
The filter is also the cheapest insurance against the most common failure on this housing stock. A restricted filter drops airflow across the evaporator coil; low airflow lets the coil ice; an iced coil means the system runs continuously and cools nothing. In a 1970s Longwood plan with a single central return, the return path is already the tightest part of the system, so it does not take much restriction to get there. What that looks like.
Two related notes. A very high MERV filter in a system not designed for the pressure drop can cause the same problem as a dirty one — match the filter to the equipment rather than buying the highest number on the shelf. And if the filter is at an attic air handler rather than a wall grille, put a reminder somewhere you will actually see it, because out of reach means out of mind. Attic air handlers here.
Sources
- NOAA 1991–2020 climate normals, Orlando station. https://www.ncei.noaa.gov/products/land-based-station/us-climate-normals
- U.S. DOE, 2023 Central Air Conditioner Standards FAQ. https://www1.eere.energy.gov/buildings/appliance_standards/pdfs/2023_CAC_Standards_FAQ_10-5-2022_Final.pdf
- Seminole County Property Appraiser CAMA extract (Parcels.csv, dated 5 September 2026), tax district L1 — Longwood; improved residential parcels, DOR codes 01 and 04. https://www.scpafl.org/
- City of Longwood FAQ: “Do I need a permit to remove a tree?”. https://longwoodfl.org/FAQ.aspx?QID=163
Figures are dated. Permit fees, rebate amounts and code cycles change — re-check the primary source before you rely on a number here.
Ask us to show you where the filter is
On an attic system it is not always where people assume, and a filter nobody can find is a filter nobody changes.