If you have a popular filter size you're likely to find that you have many options to choose from. This guide will help you identify the important differences between filters.

MERV Rating

The most obvious difference between filters is usually the MERV rating.  The MERV rating is a complex and technical topic, but in a nutshell filters with a higher MERV rating will filter more stuff from the air than will a filter with a lower MERV rating.  For residential use the MERV rating will be between 1 and 16.

Change Frequency

Different filters may have different recommended change frequencies.  Most 1" filters should be changed every 1 - 3 months, while 4" and 5" filters can last up to 9 - 12 months.

Washable

Some of the popular filter sizes will have washable filter options.  The tradeoff with washable filters is that you may never have to replace your filter, but you cannot get high levels of filtration (high MERV ratings) from them.

Carbon Impregnated

Some filters are coated with activated carbon to absorb odors as the air from your house passes through the filter.  These filters provide adequate filtration with the added benefit of odor blocking carbon.  If you have pets or other sources of odors in your house you may want to consider a carbon filter.

OEM and Non-OEM

When you have a separate air cleaner installed in your HVAC system you may find both OEM (Original Equipment Manufacturer) and non-OEM options available.  OEM means that the filter was made by the same company that made your air cleaner, while non-OEM means that the filter was made to be a physical match to the original filter.  Non-OEM filters offer a variety of features that may not be available from the manufacturer, such as higher/lower MERV ratings, easier-to-change design, or carbon odor block.