How Often Do You REALLY Need to Replace Your HVAC Filter?
Do I have a story to tell you about HVAC filters—another lesson I’ve learned the hard way so you won’t have to. Truth be told, if my faux pas helps you avoid a huge expense, I’m happy to have suffered it.
While researching to help a reader solve the mystery of grimy black lines around the edges of his home’s carpet, I casually asked my husband if he’d recently replaced the filter in our heating ventilation air-conditioning (HVAC) system. I got one of those blank stares I could easily translate: Nope, didn’t even think about it.
When we bought this house, we had the HVAC system inspected and serviced and the filter replaced. Then we got busy with leasing it while we planned and executed our big move a year later. HVAC filter? Completely forgot about it. It had been more than 2.5 years since I brought up the subject!
The scariest thing ever was to open that door on the HVAC system, dutifully labeled “Filter.” I cannot adequately describe it but I can tell you that it was nearly black and covered in what looked like fur. So gross. I’m surprised the entire system didn’t just blow up out of sheer rebellion for lack of attention.
I have since learned about the true cost of a dirty HVAC (heating, ventilation, air-conditioning) filter and it’s not pretty!
The True Cost
High energy bills
While the heat, ventilation or air-conditioning is running, 100% of the air in your home passes through a filter, typically twice every hour. When the filter is clean, the air passes through easily. But if the filter gets clogged up with all the stuff it’s filtering out, the system has to work much harder to keep air moving.
The dirtier the HVAC filter, the less efficient the system can be—and more likely to develop problems. According to the Department of Energy, regular filter changes can reduce your energy bill by 5% to 10%. Conversely, a dirty filter will send that bill through the roof!
Family health
A quality filter captures the harmful bacteria typically found in sneezes, coughs, viruses and molds, and pollutants like dust and car fumes that come in through doors and windows.
If you have allergies or asthma, indoor air pollution can trigger your symptoms. According to medical professionals, most people don’t realize that indoor air pollution levels are much higher than outdoors—two to five times higher.
When particles become airborne, you can breathe them in and experience an allergic reaction. The heating, ventilation, and air conditioning (HVAC) system in your home can harbor and then spread mold and other allergens.
Grimy, dark carpet stains
It’s called filtration soiling and shows up as dark, shadowy, dirty lines on the carpet along baseboards, under doors, beneath draperies, along the edges, and in the crevices of carpeted stairs.
Filtration soil is as ugly as it is gross and comes from airborne pollutants passing through the carpet as the air is drawn through the crack between the carpet and the baseboard, around the drapes or under a closed door.
It’s an accumulation of soot from dirty ducts, smoke from candles and the fireplace; tobacco, kitchen grease from the oven and cooktop; smog, auto emissions, and pollutants from outdoors.
The way it’s supposed to work is that all of that stuff in the air gets trapped in the system’s air filter. But once the filter is full, the system will send the air pollutants back into the house through the ducts, where all that icky mess gets lodged into corners and crevices.
The Simple Solution
Change the HVAC filter often
Check at least once a month, more often during heavy-use months (winter and summer). Keep in mind that some systems have multiple filters. Take some time to research your system to discover exactly what and how many filters you have.
If the filter looks dirty after a month (it is no longer white) change it. Homes with pets, multiple occupants or when located in regions with general air pollution, may require more frequent changes. At an absolute minimum, the filter must be changed every three months.
A dirty filter will slow air flow and make the system work harder to keep you warm or cool, wasting energy. A clean filter will also prevent dust and dirt from building up in the system leading to expensive maintenance and/or early system failure.
Calculate
Mark your calendar. Set an alarm. Do something that will trigger your memory to check your filter so you can get to the store to buy a new one. Or a bunch so you have them on hand.
Don’t assume you’ll just remember. You probably won’t until one day, 2.5 years from now you notice your utility bill has shot through the stratosphere, you have this weird cough or you see odd, dark shadows forming along the edges of your carpet. Don’t let that happen.
Automate
My filthy filter wake-up call prompted me to get online to do some research. That’s how I found FilterEasy, a company that delivers the exact HVAC filter we need, just when we need to change it—at a comparable cost to the same filter at the home improvement center store near our home. Wow! What a great service for those of us who need reminders. I don’t have to think about when to replace the furnace filter.
I set up an account online and identified the exact filter we need (they’re listed by size—including custom sizes if the filter you need is not standard) and the delivery frequency. All that took about five minutes. Now I can forget because I’ve put FilterEasy in charge of remembering.
We received our first shipment. Having that compact box show up at the door was a reminder that we needed to replace the filter. Done.
You can probably beat the Second Nature price if you buy filters when they’re on sale and are diligent in sticking to your own rigid maintenance schedule. For some of us, a subscription plan with FilterEasy is an absolute bargain given the high cost of failure to stay on top of this critical home maintenance issue.
Some products displayed in this post may earn us a commission. Why trust us?
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When my system stalled, the technician told me that the HVAC filter’s purpose is to protect the motor, not to cleanse room air. My system quit because of using medium MERV filters, even changed frequently. Best to use a flat, not pleated, filter, and buy a separate air cleaner. PS..Love your daily emls & tell friends.
Hi! At this time we have 2dogs, & 3birds(in cage) in our house & chng air filter monthly. This past summer we had problems with water abundance in air filter resevoir. Repair bill was high 2mo in row …froze up & water accumulated. I have found I have to turn off system to put in filter but really struggle to take out old one first. It is not terrible looking(filter) when I chng monthly but want to because of allergies/sickness…we also live in country on small acreage with lots of animals outside. The filter goes in horizontal different from what shows on pkg. …do you have any suggestions to better get out the filter?
Are you certain you are using the right size filter for your system?
I’d also make sure that when you turn the furnace off to change the filter, make sure that the FAN has ALSO shut off–the fan itself sometimes runs for several seconds after you’ve shut off the furnace/air conditioner, and it can exert a tremendous vacuum pressure on the filter. Mine gets suctioned into the filter frame TIGHTLY, until the fan shuts off, and then it almost drops out by itself. Good luck!
Hi Mary, thanks for sharing this informative article. Ours would light up red too if it’s time to clean filter and red light would automatically off once it’s cleaned or changed! Old and dirty filters is also one of the reasons why our ac is not blowing cold air.
I change my filter monthly as recommended by my HVAC technician. When I receive the utility bill (monthly) I use that as a reminder to change the filter.
Do you also subscribe for their frig water filters? The name brand filters are expensive yet you want a good filter that matches their quality.
Wanda
I do, Wanda. It’s becoming more difficult to find the right ones, and delivery times can be iffy.
Hello Mary,
A helpful hunt: I also write the date on the side of filter when I change it so I know exactly when it was changed.
Great tip! Thanks …
Our thermostat has a reminder option. Every thirty days a red light alerts us to a message on the thermostat. I can use the touchscreen to tell it I’ve changed the filter or to remind me again in X days. I need that annoying red light to remind me to change the filter.
Well now, that’s a nice feature!
You can buy a permanent filter that needs to be cleaned and really save a ton of money over the years. Mine cost about $85 15 years ago.
Are the cheapest air filters in the store adequate? Or is it worth it to spend more? We have no pets and no allergies. Thanks Mary!
They are certainly adequate, Jane. Making sure you have the right one on a routine basis can be the challenge.