There are many levels of furnace filters. I can get cheap ones at walmart of a few bucks. Then there are ones that cost upwards of $30. I realize that if you have allergies or low immune systems, these are probably worth it. Also if you have pets they may help. But for average folks, with no medical needs, are they worth the cost?
Are High End Furnace Filters worth the cost
air-filterfurnacemaintenance
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Dirty filters not only make the HVAC equipment not last as long, but the low air flow makes them less energy efficient. A dirty furnace does not conduct heat into the air as well and the dirt sticks to the fan blades making it not last as long or spin as easily.
There are two main types of air filters:
The 1" thick ones that look like this:
And the 6" thick filters look like this:
(source: filterscanada.ca)
Generally the 1" filters are good for a month or two. The 6" thick ones are good for 6 months.
There are also 2", 4", and 5" filters available but generally not at the local hardware store. Some folks who have 6" filters use a 2" + 4" filter and replace the 2" one every other month and the 4" once a year. This seems like a hassle to me, but it might save you $50 a year if you have 6" filters.
The thicker the filter, the more area can be created within the filter by folding the filter materials into baffles. This creates a very high efficiency filter, but I don't think I've ever seen one this thick stocked in a store. I'm sure you could resize the opening for a thinner filter, but if it was my choice, I'd order the thicker ones online.
The same thing happens in other places, e.g. high efficiency toilets have a larger flapper than what is typically stocked in stores, which will make getting replacement parts a pain.
Best Answer
The problem with the really cheap filters is that you really should replace them monthly. The slightly more expensive filters often only need to be replaced every 3 months or so, which in reality doesn't actually make them that much more expensive.
I usually go with the cheapest 3 month filters, since I know I'm not going to get down there every month to replace the super cheap ones. Aside from that consideration and the ones you already mentioned, there's no need to spend lots of money on a top of the line filter. They aren't going to make your furnace last any longer.