PadMatch / Every humidifier water panel and furnace filter size
- Humidifier pad
- flat evaporator panel, e.g. AprilAire 35 at 10 x 13 x 1.75 in, swapped once per heating season
- Furnace filter
- pleated air filter, e.g. 16 x 25 x 1 at actual 15.5 x 24.5 x 0.75 in, changed on a MERV-dependent schedule
- Job of the pad
- wick water into the airstream to raise humidity
- Job of the filter
- trap dust and allergens to protect the blower and clean the air
- Interchangeable
- no; different size, different slot, different job
Why the humidifier water panel and the furnace air filter are not the same part.
A whole-house humidifier and the furnace air filter both live on the same air handler, so they are easy to confuse, but they are separate consumables. The humidifier pad, also called a water panel, is a thin evaporator that water trickles over to add moisture to the heated air.
The furnace filter is a pleated panel of media that the blower pulls all the return air through to trap dust, pollen and finer particles. A humidifier pad does not filter and a furnace filter does not humidify, and neither one fits the other's slot.
Both are annual or seasonal parts, which is the only thing they share. Match each to its own model number: the humidifier by its Aprilaire or Honeywell humidifier model, the filter by its nominal size and MERV.
Find your model
Read the number stamped on the humidifier cabinet or printed on the old pad, then match it below. Confirm the frame size before buying a generic.
- AprilAire 35 humidifier water panelthe common humidifier pad
- 16 x 25 x 1 furnace filterthe common furnace filter
- MERV 8 vs 11 vs 13which filter rating to buy
Sources: AprilAire Water Panel 35 product page · Atomic Filters nominal vs actual air filter size chart · American Standard: furnace filter sizes explained