Filters are one of the most common questions I get from customers:
"What kind of filter should I use?"
There are many different filter manufacturers and types of filters. Do not use highly restrictive filters. The filters $15.00 - $25.00 are typically too restrictive. The air conditioning manufacturer engineers design these machines to remove heat and moisture from your home. They design them to run at a range below .5 total external static pressure in inches water gage. What that means in English, the air needs to move through that machine at a certain level of resistance. If you have every had a nice, thick milkshake, you know you really need to pull on that straw to get your yummy. Then if you switch straw to a coffee straw - you are not going to get your yummy. You cannot overcome the added resistance. Don't add resistance to your air conditioner, that it is not engineered to overcome. With that said, an inexpensive 1" pleat with 1 pleat per inch or so will be adequate. Have your air conditioner maintenance service 2 times a year to keep coils and drain system clean. My technicians have a meter to test the resistance, if you would like.