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:

Great for New Homes

A companion app sends notifications when its time to replace this one, which comes in a set of a half-dozen. Filtrete

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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.

For Houses with Carpeting

This choice can capture dander from dogs and cats, and is made in the USA. FilterBuy

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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.

Best for Pet Owners

This option is fine enough to trap smoke particles, as well as pollen and dust. Filtrete

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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.

Multiple Sizes Available

This model can be used in both central units and wall units. Filtrete

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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.