General Question

I have a Carrier furnace. It takes 20x25x5 air filters. Does it really matter what brand filter I buy?

90 replies
  1. 1
    Steve from Antioch says:


  2. 2
    gogol's wife says:

    I never heard that brand mattered. Size matters.

  3. 3
    FarmerG says:

    I buy them a dozen at a time online. Much cheaper and you tend to remember to replace them more regularly when you have them on hand.

    There are levels of filtration that may be a factor for you but I find the normal pleated ones work well and I have two 60 lb. dogs and three cats.

  4. 4
    CarolDuhart2 says:

    Not really. As a condo owner, I have had a maintenance guy put them in, and later when he stopped doing that, I started to buy my own-and it doesn’t matter at all, as long as it fits.

  5. 5
    namekarB says:

    From the first Google hit when I typed “What is the best furnace filter?” Yeah. Really. Have you ever tried Google?

    The choice of which filter to buy for your furnace depends on how much you want to spend, what you’re trying to filter, and how diligent you are about changing the filter.

    The minimum efficiency reporting value (MERV) scale goes from 1 to 16. Most residential filters range from 4 to 12. Furnace manufacturers prefer the traditional spun fiberglass filters (MERV 2) because they filter out enough of the large particles to protect the furnace while providing maximum airflow. Maintaining the furnace manufacturer’s specified airflow is critical to achieving energy efficiency and maximum life from the blower motor and heat exchanger. An inexpensive MERV 4 filter captures 80 percent of the particles 50 microns and larger, but only 25 percent of the particles in the 3 to 10 micron range.

    For most homeowners, a more expensive MERV 7 or 8 pleated filter provides a good balance between cost and filtration efficiency. These filters trap 80 to 95 percent of the particles 5 microns and larger—more than enough filtration for most households.

    Furnace efficiency is one thing. But if you’re a clean freak or have family members with allergies or low-immunity issues, spend more on a high-efficiency (MERV 11 and higher) filter. Then just make sure you stay on top of filter changes to protect your furnace.

    High-efficiency filters capture 99 percent of airborne particles as small as 0.3 microns (bacteria and viruses, fumes and pollen). But you’ll have to run your furnace fan full time to get the maximum benefit from a high-efficiency filter, and that will cost more. Figure the extra cost into your decision.

    Finally, never switch from a fiberglass filter to a high-efficiency filter without first talking to your HVAC technician. The technician can boost fan speed to compensate for the reduced airflow. Even then, you still have to be diligent about replacing the filter regularly. A clogged filter can burn out the blower motor, damage the heat exchanger and cost you hundreds of dollars in wasted energy.

  6. 6
    redshirt says:

    Great topic Cole!

  7. 7
    I'mNotSureWhoIWantToBeYet says:

    Don’t fall for the thinking that cost or brand is most important. Look at the MERV filtering efficiency. Bigger numbers might sound like the way to go, but it really depends. The fan has to work against the filter. If the filter is too wonderful about grabbing small particles, you’ll get less airflow. So your home may feel more stuffy or the temperature may be less uniform, etc., etc.

    I installed filter grills on our return vents a few years ago. It’s great for increasing the life of the main filter. But having high number filters on the main filter and the return dramatically cut down the airflow. So I need to use lower number filters on the intake and main filter than I would have otherwise, and probably replace them more frequently (every 3-4 months rather than every 6-9+ months).

    I generally use 3M filters, but some I can only find in other brands.

    Here’s a more technical discussion of what’s been reported in the scientific literature.

    HTH a little.


  8. 8
    JPL says:

    I use 3M filters that last 3 months. I hate going into the attic to change them.

  9. 9
    JPL says:

    John, Even if you buy a filter that says three months, you should change it after two. You have a menagerie in your house that clog the filter.

  10. 10
  11. 11
    gogol's wife says:

    I hate to say it, but you bigfooted yourself.

  12. 12
    p.a. says:

    @JPL: yes. don’t forget to clean the return vents.

  13. 13
    Eric U. says:

    3M probably makes most of them. Except for the charlatans

  14. 14
    Satby says:

    Nope. I buy the higher filtration ones to clean out the incredible dust/fur/dander around here, but I change them about every 6 weeks or so even though they’re supposed to last 3 months. I also vacuum the floor vents.

  15. 15
    Jade says:

    If your furnace is under warranty using non carrier filters void it. Keep a Carrier to plug in before you call the repairman.

  16. 16
    ARoomWithAMoose says:

    HEPA seems to matter less than swapping them out often. Given the fleet of animals you have get the cheapest paper ones that don’t collapse (not the old stlye fiber glass ones) and change them out at least monthly.

  17. 17
    muddy says:

    X5? Wow. I never saw any over 2″ thick.

  18. 18
    FlyingToaster says:

    Size and filtration level matter; brand doesn’t. I get mine at either HomeDepot or Target in the 3-pack, whichever has the right sizes in stock. I change mine twice a year; so does the HVAC company, so it gets the every-three-month switch. But I don’t have furry pets.

  19. 19
    Ruckus says:

    @gogol’s wife:
    Damn and all this time I’ve been told that size didn’t matter.

    The subject matter may have been different though.

  20. 20
    I'mNotSureWhoIWantToBeYet says:

    @muddy: Ours is 4″ thick. It’s an old Honeywell electrostatic filter. I pulled out the two electrostatic modules (which still work but don’t seem especially effective) and replaced them with a 4″ wide HEPA filter that fits fine.


  21. 21
    ThresherK says:

    After years of the throwaway ones I splurged on a 25-25-4 with a washable model. Note that this was in our old house and we were only there for 8-9 months before we moved. No idea if current owner has customized it.

    The rinsing and drying was no trouble if you have a big enough tub / shower with a detachable head for precise rinsing. Otherwise it’s like trying to wash a full-grown golden retriever in the kitchen sink.

    Current condo has an electrostatic thingy I rinse quarterly.

  22. 22
    BubbaDave says:

    @gogol’s wife:
    That sounds like it should be a euphemism for something.

  23. 23
    Rob says:

    What namekarB says in post #6, especially this
    “Finally, never switch from a fiberglass filter to a high-efficiency filter without first talking to your HVAC technician.”

    I have a Carrier furnace and was never told by the HVAC company which installed it to use Carrier filters. I use 3M pleated filters.

  24. 24
    gogol's wife says:


    we’re talking about filters

    I love that this post is in “Science and Technology.”

  25. 25
    gogol's wife says:

    Don’t more people want to suggest “best post of the year” in the thread below?

  26. 26
    father pussbucket says:

    Just click on the ad at the top.

  27. 27
    Ruckus says:

    @gogol’s wife:
    Size could be a filter.

    Just saying.

  28. 28
    p.a. says:

    @I’mNotSureWhoIWantToBeYet: I have a Honeywell e-filter. They suck to clean. I may go replacement with a passive filter myself.

  29. 29 says:

    I had a conversation with a trusted a/c guy recently about filters. Brands don’t matter. He also said don’t waste your money on the expensive filters but don’t get the cheap ones that you see at dollar store kind of places. He said to get a couple of levels up from the cheapos but to change them every month(AZ is dusty.)Your a/c unit will last longer.

  30. 30
    I'mNotSureWhoIWantToBeYet says:

    @p.a.: I thought our electrostatic filter was working the way it should – lots of black stuff always came off when I sprayed it off in the laundry sink. But when I had a HVAC guy out to recharge the freon in our AC circuit, he showed me the buildup on the furnace fan and said they really don’t work that well. I went to the HEPA filters a few months later. They seem to help in the spring and summer when the pollen around here is extreme (yellow car in the mornings, etc.). But the ~ $25/ea cost is a bit of a pain…


  31. 31
    redshirt says:

    @gogol’s wife: Cole’s scintillating double posts killed discussion for the moment. Let’s wait for Anne or Betty to get things started back up.

  32. 32
    NotMax says:

    Real men smoke non-filters.


  33. 33
    muddy says:

    @NotMax: I remember when that was the only choice in Camels. Now there are about 20 varieties I guess.

    There are too many flavors over everything these days. Some should clearly be eliminated.

  34. 34
  35. 35
    Suzanne says:

    We don’t have. Furnace, we have a combo A/C and heater, but the principle is the same. The brand doesn’t matter. We were using HEPA filters, but they lower your energy efficiency.

  36. 36
    Villago Delenda Est says:

    @namekarB: THIS is a very helpful and informative post! Thanks!

  37. 37
    Villago Delenda Est says:

    @gogol’s wife: The important thing to ask is if Redshirt gave Cole permission to bigfoot himself.

  38. 38

    @namekarB: This, definitely. Cheap can hurt, better to go for what is designed for the furnace. Buy an armload, mark the date on it when you install it, change it regularly, blah blah blah.

  39. 39
    redshirt says:

    @efgoldman: A Viking Longboat of clogged HV/AC filters is such a beautiful image.

  40. 40
    Rashi says:

    “This post is in Science & Technology” Maybe the funniest thing written on this blog ever.

  41. 41
    Amir Khalid says:

    @Villago Delenda Est:
    Say that Mad Max: Fury Road is the bestest movie ever made, and I suspect Redshirt will forgive you anything.

  42. 42
    muddy says:

    @redshirt: Exactly.

    I was asked to bring a side dish to dinner with roast ducks. There will be potatoes and brussels sprouts. I’m very tired and not feeling creative. How great it would be if everyone gave me suggestions…

  43. 43
    redshirt says:

    @Amir Khalid: It surely is not, but maybe in the top 1000 of all time?

  44. 44
    redshirt says:

    @muddy: To the sickos at Modern Bride magazine: For shame!

  45. 45
    NotMax says:


    Orange glazed carrots.

    Or maybe couscous with mushrooms.

  46. 46
    raven says:

    @muddy: Duck gumbo

  47. 47
    muddy says:

    @NotMax: No couscous because no wheat. No dairy. Or sugar (raw honey and maple syrup excepted). No nightshades (yes I know potatoes are nightshades). No mushrooms. No mint or other salicylates. No soy. The hostess is somewhat orthorexic.

  48. 48
    Origuy says:

    @muddy: Wild rice. It’s grown in marshy areas where ducks live.

    ETA: Pure wild rice is gluten free; some mixes will have soy or gluten.

  49. 49
    muddy says:

    @raven: They are roasting the ducks, after presumably steaming them.

  50. 50
    Mary G says:

    I don’t have a furnace, just two wall heaters. This is one of the few times a year I wish I did, but I have a flat rock roof so nowhere to put the ducts. It’s cold today, only 59. Now you can all yell at me.

  51. 51
    raven says:

    @muddy: Save the fat.

  52. 52
    muddy says:

    @Origuy: At first we were going to have wild rice I was told, and it wasn’t a hybrid (of course because normal rice has arsenic, never mind the gluten), but it was changed to potatoes. Roasted, always roasted.

    Jeez, I thought I was feeling tired because I’ve been working 2 different busy seasons. Now I realize I felt extra tired about coming up with a dish because nothing will fit the demanded criteria.

  53. 53
  54. 54
    raven says:

    Norwood punked everyone!

  55. 55
    Tom says:

    Just Apollo 13 it and duct tape a tshirt over it, voila! Filter.

  56. 56
    NotMax says:

    Sigh. Bad code fix.


    If honey is okay, maybe this carrot recipe.

    Or this one.

  57. 57
    muddy says:

    @raven: Oh yes! I recently got a number of moulard magrets at a very good price and carefully saved the fat. I was going to cook with it, but then I found out it was a terrific substitute for butter on toast.

    It didn’t last long, I was immoderate.

  58. 58
    Ruviana says:

    @muddy: Bring water.

  59. 59
    NotMax says:


    Panty hose instead of a T-shirt. :)

    (Bonus would be reading the tale of Mr. Cole’s shopping expedition for that item.)

  60. 60
    WaterGirl says:

    Hmmm. I haven’t changed my filter in two years. After reading this post and seeing the comments, I am beginning to think that I may not be changing mine often enough. Really? Every 3 months? Yikes!

    I’m sure having 2 dogs and 2 cats helps. oops

  61. 61
    raven says:

    @muddy: Whoo hoo!

  62. 62
    muddy says:

    @NotMax: The first ones worked, at least after you reposted? Perhaps it was retroactive.

    I like the look of that first one. Not roasted is a plus, just for the variety.

  63. 63
    FlyingToaster says:

    @muddy: Sweet potatoes? Green Beans? Arugula salad?

    In your shoes, I’d probably cancel due to contradictory requirements [edible by humans yet meeting the hostess’ exacting standards]. But I’m mean like that [I can make gluten free or I can make light and fluffy — you cannot have BOTH].

  64. 64
    muddy says:

    @Ruviana: That’s about the size of it, although of course I would be challenged as to its source and container.

    Maybe a really simple salad. I made some cherry balsamic vinegar this year that would be very nice.

  65. 65
    ThresherK says:

    Any ideas on how to add bacon and a smidge of bacon grease to a peanut butter (and perhaps chocolate) recipe?

    I’m thinking cookies, bar / drop / slice dough.

  66. 66
    muddy says:

    @FlyingToaster: Can’t, it’s family Christmas. Local.

  67. 67
    muddy says:

    @ThresherK: I guess the bacon would want to be cooked first? And you’d need more flour to sop up the extra fat perhaps. I don’t bake much. I make a peanut butter cookie that is just peanut butter, brown sugar and baking powder. The dough is very very soft.

    Last year I cooked thick local bacon crusted with maple sugar, that was a nice “candy”.

  68. 68
    J R in WV says:

    I try to get high levels of filtering and then I want to change them out monthly.

    Dogs and cats, dusty house.

    ETA: Menu item suggestion. Last night at the Solstice dinner, there was a great fruit salad. Shopping wisely for good fresh fruit, no creativity otherwise. Peeling and slicing, no problems with the menu restrictions, which seem crazy to me, but whatevers.

  69. 69
    rikyrah says:

    I don’t know about different kinds of furnaces, but I will say this…years ago, I ‘ upgraded to those fancy, $6/7 a piece air filters, and I wasn’t getting any heat in my house. Call the furnace man, pay him $100 for him to tell me that if I want some heat, I better go back to those ugly, generic, blue-colored $1.85/ a piece air filters. More expensive doesn’t always mean better. Maybe the fancy ones work in your furnace, Cole. But, they don’t work in mine.

  70. 70
    rikyrah says:

    Rev. Run knows how to keep himself a tv show. Now, he’s got the one on the travel channel, and I just watched all the episodes so far. I loved the family’s trip to Hong Kong. The tailor was hilarious. And, the image of Rev. Run, going to this hideous looking building in a bad looking part of Hong Kong, only to open the doors to find this fantastic looking indoor skateboard park and game place – with two young entrepreneurs who obviously LOVED hip-hop and were gobsmacked to have THE REV RUN of RUN DMC in their business..I loved it..LOL

  71. 71
    sacrablue says:

    @muddy: Roasted carrots with honey and thyme

  72. 72
    sacrablue says:

    @sacrablue: Since I can’t edit, never mind. NotMax got to a recipe before I did.

  73. 73
    Lolis says:

    I use these re-usable metal filters. They are made in the USA and supposed to last a lifetime. So far, so good. It is an investment but good for the environment and cheaper after a few years of disposable filters.

  74. 74
    rdldot says:

    @muddy: roasted acorn squash w/cumin/coriander. google recipe at martha stewart.

  75. 75
    Ruckus says:

    Sniff, sniff. Now I’m being sent out to sea on a dirty chunk of ice? When did I turn 103?

  76. 76
    ThresherK says:

    @muddy: Well, my go-to for bacon and chocolate is Alton Brown’s chewy-chocolate-chip recipe with some bacon in it.

    I cook the bacon in a slow oven, pour off the fat, mince the bacon really, really finely, and then I scrape the bacon fond off the sheet pan. (Really, that stuff is incredible.)

    I find that substituting 1/4 of the butter with bacon grease is just the right amount of bacon flavor, makes the math easy, and doesn’t lead to too much spreading. But I do toy around with less white sugar and a touch more flour, on the “don’t spread too much” front also, plus freezing or chilling the dough.

    But the texture of peanut butter is a whole new thing, and I don’t know if the regular PB-with-Hershey’s Kisses takes adding the bacon well.

  77. 77
    Ruviana says:

    @muddy: Maybe you could just take the vinegar.

  78. 78
    raven says:

    @rikyrah: What’s to work?

  79. 79
    muddy says:

    I appreciate all the suggestions.

    @ThresherK: The bacon cookies sound good.

  80. 80
    muddy says:

    @Ruviana: As it is I will need to be vague about what sort of balsamic vinegar it was before it had the cherries in it.

  81. 81
    rikyrah says:


    I order them – $25.00 for a box of 10 at Home Those ugly,look like they’ll break at any minute blue air filters.

  82. 82
    gogol's wife says:


    That’s what we use. It’s not a Carrier furnace, but it was a good one when I bought it. I get it serviced every year, and the guy doesn’t seem surprised about the filters.

  83. 83
    Ruckus says:

    Someone else is going to row the damn thing……. aren’t they? I’ve been to sea before, 75,000 shaft hp. Or at least the wind, in my sailboat. Rowing sucks. At least with the ice you froze off your ass first thing and there’s no rowing.

  84. 84
    catclub says:

    Are there really 5 inch thick filters?

  85. 85
    Gvg says:

    Do you have allergies? I have to use the fancy high efficacy ones or wake up with burning eyes, sinus headaches and a sore throat. My sister also. Our parents on the other hand have never had symptoms and have to be reminded to change theirs when we visit. It varies. You may not have as many choices with the new thick style. Our new air conditioner takes an odd size I have to order online anyway.

  86. 86
    seaan says:

    BTW – there is a fairly simple solution for those who hate going into the attic or basement to change furnace filters. There are return air-vents that hold a filter, and so long as it is not in a ceiling or something, they make it much easier to change the filters (just search on “return air filter grille”). Also, for my home anyway, they had an additional benefit of helping reduce noise (fan noise about the same, but noticeably less air turbulence noise).

    We normally use a higher MIRV filter, changing every 3 months. But they had been getting more expensive at Home Depot (and our current setup has two smaller filters, each of which cost the same as a single larger filter with the same square area). So this year I tried an internet firm, after some research went with a bulk buy from Filters Fast. Works OK so far (only 2 months into the season though). My only complaint so far is their spamming email. I set my preference to weekly, but was still getting emails daily. So my advice is to decline any regular email.

  87. 87
    Scapegoat says:

    Tired of getting sick? (Ha!) Got lots of pets? (Double-Ha!)

    Buy the most expensive filter you can afford to change (or wash) every six to eight weeks.

    (…and to keep those knock-down-drag-out colds away, take one dose of grape seed extract per day. This “one neat trick”, from an M.S. sufferer changed my life — six years without a cold while teaching.)

  88. 88
    Prescott Cactus says:

    @ Scapegoat: take one dose of grape seed extract per day

    Like filters, size matters.

    100mg. . . 300mg. . 1 drop ?

    Please !

  89. 89

    Yes, it matters a lot. We have a furnace that takes 20x25x5 filters, but the actual size is 19-3/4×24-3/4×4-3/8. When I was looking for replacements, I found about 10 different sizes of “20x25x5.” Make sure you get the actual size for your furnace.

  90. 90
    bobbo says:

    No, but beware of super duper high rated ones that filter out everything. My motor wasn’t powerful enough to suck the air through the filter and eventually it burned out the alternator. (Excuse my mechanical ignorance if I’m getting the terms wrong.) $250 was not a bad price to learn my lesson.

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