Replacing the air filter in your furnace is one of those jobs that always nags at the back of your mind. Like getting your oil changed or fixing a leaky faucet, you know you should do it, but it always seems to end up low on your priority list.

Of course, never getting your oil changed will ruin your engine, and a leaky faucet can end up wasting gallons and gallons of water each month. In the case of your air filter, letting it go too long without attention wastes energy, damages your furnace, and may prove a whole lot more expensive than you realize.

Let’s dig in deep to see why your air filters deserve to be a high priority.

What Air Filters Do
Put simply, air filters keep your furnace clean. They do it by catching the dust, hair, and particles that would otherwise build up inside the system. Without it, all those particles end up in the furnace itself and impede the air flow. That leads to an inefficient system, and those inefficiencies have a funny way of showing up on your energy bill.

How Air Filters Work
As your furnace circulates the air through your home, it also picks up foreign particles and dirt. Air filters protect vital components by keeping that junk from building up inside the furnace itself. An air filter is essentially a fine mesh screen. As air from the house passes through the screen, particles get caught in the filter.

Left unchecked, these particles build up until eventually the filter is too thick with grime to let air through easily. The blower and other components have to work harder and harder the longer the filter goes unchanged.

Size Matters
In the case of air filters, bigger isn’t better. It might seem logical that a 5” thick air filter would need to be changed less often than one that’s only 1” thick. But unless your furnace is designed for a thicker filter, its blower motor isn’t up to the job. The strain caused by an oversized filter can even cause your blower motor to burn out. That’s going to cost you a lot more money than just replacing the 1” filter on a regular basis.

Trust the Professionals
If you’re still feeling a little unsure about when to change your air filters or what kind to use, we recommend that you ask a professional. Make sure they’re North American Technician Excellence (NATE) certified, too—that way, you can rest assured you’re getting an expert opinion.

Another professional you can trust? Your Energy Advisor. If you’re worried that your furnace is losing efficiency, a home energy audit can help you figure out why.