You might have trouble selecting the right 20x24x1" due to the number of affordable and highly rated choices.

The MERV 13 Pleated Filter is electrostatically charged and captures airborne allergens smaller than one micron. The chemical-free filter is more than 30 times more efficient in capturing micro particles than ordinary fiberglass filters. It's effective at capturing particles ranging from viruses to pollen to pet dander.

Another contender is the MERV 11 Pleated Filter that comes in a six-pack. It can last up to four times as long as standard panel filters. It has a large surface area to maximize its effectiveness while minimizing airflow restriction.

The MERV 8 Pleated Filter is excellent for high-velocity equipment. It will protect your system from developing mold, mildew, bacteria or other microorganisms. The filter is listed and rated by Underwriters Laboratories as U.L. Class 2.

Don't want to buy a disposable filter? Then you'll want to take a close look at the MERV 5 rated permanent washable filter. It's easy to install and maintain. You clean it simply by backwashing it every month with cold water. The filter is interchangeable with standard one-inch filters.

Fiberglass 20x24x1" Panel Filter is a one-month filter that comes in a 12-pack, giving you a full year of filter coverage. It can be used as a prefilter to extend the life of a higher efficiency filter.