How to Choose a Furnace Filter

A few notes on finding the right furnace filter for your living space and comfort.

Woman changing air filter
A quality air filter will keep dust out of your home and your furnace running as efficiently as possible.Filtrete

The best thing you can do to keep your living space comfortable, and your furnace running well, is to change the furnace filter regularly. A clean filter allows more efficient movement of air through the furnace and thus your entire living space, so it will reach and maintain the temperature you want quickly and efficiently. Not only will you be more comfortable, it also means the furnace won’t have to run long or often, reducing energy consumption and cost. It also prolongs the life of the furnace.

Filters serve the important purpose of trapping dust, pet dander, and possibly allergens and other particles, so you don’t want to skimp on quality—but you also don’t want to spend money on a filter that you don’t need.

Furnace filters have various rating systems, but the most common one is MERV, which stands for Maximum Efficiency Reporting Value. MERV ratings vary from 1 to 16. The higher the MERV, the denser the filter. But the denser the filter, the more the furnace has to work to pull air through it, so you don’t want to get a filter with a MERV rating that’s too high. Some manufacturers add other features to filters that are supposed to attract dust, thus increasing the capability of the filter without increasing the MERV rating.

What’s the best furnace filter for you? That depends on your house, what’s inside it, and your comfort level (and whatever the furnace manufacturer may recommend). Here are four typical scenarios, along with the type of filter to choose for each:

You have a newer or otherwise well-sealed house, with no pets and little or no carpeting

Filtrete 16x25x1, AC Furnace Air Filter
The Filtrete Allergen Defense furnace filter is equivalent to MERV 11, adding an extra level of air cleaning.Filtrete

Modern homes are marvelously efficient, with good insulation and tight-fitting windows and doors. Besides reducing energy consumption, that also equates to less outside air being allowed in, along with various particles. Pets give off dander, hair, and outside dirt. And carpets slowly break down, emitting dust particles. So, having no pets and little carpeting means fewer particles in the air overall. A furnace filter with a MERV rating at or near 5 will do the job here.

Your house is neither new nor old, you have a pet, and some carpeting

FilterBuy 20x20x1, Pleated HVAC AC Furnace Air Filter
FilterBuy’s MERV 8 furnace filters will trap pollen and pet dander as well as dust.FilterBuy

Step up the MERV rating of your filter to 8 or so, in order to trap more particles. If you find dust accumulating over time, or if you or a family member feels sneezy during winter, step up to the next level.

Your house isn’t new, you have a pet, and/or a lot of carpeting

Filtrete 20x25x4, AC Furnace Air Filter
Filtrete’s electrostatically charged Ultra Allergen furnace filter has a MERV 12 equivalency and will trap smoke particles as well as pollen and dust.Filtrete

Go with a filter that has a MERV rating of 11 so you can keep the air clear of those dust and dander particles. This will also help keep your air ducts clear of dust—which is important because ducts are difficult and expensive to clean.

You need to rid the air of smoke, or regularly have severe allergic reactions to dust or pollen

Filtrete 16x25x1, AC Furnace Air Filter
Filtrete’s electrostatically charged Ultra Allergen furnace filter has a MERV 12 equivalency and will trap smoke particles as well as pollen and dust.Filtrete

You need a high MERV, electrostatically charged filter that will capture the smallest particles. Be sure to change the filter regularly to make sure the furnace can move enough air through the house to keep it comfortable.