You might wonder why furnace filters have such a wide price range, and if you’ll get your money’s worth from a more expensive one. The short answer is that you’re getting a filter that will require changing less often and will capture more – and smaller – particles. Less expensive woven fiberglass filters do one thing – screen out dirt and debris that could damage your furnace’s blower motor – though they do remove some pollen and mold spores. If you remember to swap them out each month and air quality isn’t a concern, these will do the job just fine.

But if you’re the sort who forgets to change the oil in your car, you probably should buy a low-priced pleated filter, which requires changing only every three months. The accordion-like material in these filters features up to four times the amount of surface area in a woven fiberglass filter. This means they can capture smaller particles and for longer periods of time without impeding your furnace’s airflow.

If people in your household smoke or have allergies or asthma, or if you have pets, you might consider the more expensive, high-efficiency electrostatic filters – ones that both magnetically attract and filter contaminants. Some are effective for as long as a year. They can filter out smoke particles, bacteria, dander and odors. However, health experts warn that you might be wasting your money on these filters unless you also do the following: Install a dedicated air purifier, clean your filter monthly and use these in conjunction with a high-efficiency vacuum cleaner. It’s also helpful to take additional steps to clean up your air and house. If people you care about have respiration-related health concerns, it certainly can’t hurt.

Look for an efficiency rating

Many filters carry a MERV (minimum efficiency reporting value) rating, which indicates their effectiveness. The higher the MERV rating, the more effective. Most spun filters have a MERV rating of 4. Standard pleated filters average MERV 6. Electrostatic pleated versions start at MERV 8, with the highest quality ones hitting MERV 12.

Solving the reduced airflow problem

Pleated air filters are terrific for reducing allergens in your home. But when a homeowner leaves them in too long, they clog. Reduced airflow causes overheating and burner shutdown. When this happens too many times, the limit switch fails and the furnace won’t fire up at all. A service call and new part can easily cost you $175 or more.

Of course, no filter manufacturer can predict how long its filters will last because none of them know the dust conditions in your home. The key is to check your filter often. The rule of thumb is, “if it looks dirty, it is dirty.” If you want a smarter way to know when it’s time to replace your filter, have an air filter gauge installed. This clever device measures airflow between the filter and the furnace via a small hose.

Keep in mind that your filter works harder during the summer months! Changing your filter isn’t only a heating season chore. Many blower motors operate at a higher speed when cooling than they do when heating, meaning you should change filters more often in the summer. A clogged filter can make both your furnace and your air conditioner work harder and less efficiently.