I learned the hard way, that it doesn’t matter if you have the most expensive HVAC unit in the world, if you don’t have clean air filters, it won’t work properly. Without the air filters, the HVAC unit works horribly, and it can even quit working all together, because of the dust and dirt that builds up. My husband is always changing our air filters so our HVAC works efficiently, is cost efficient. I used to think that the air filters were too costly, so I was always trying to find a cheaper air filter for my HVAC. I went on ebay and I was buying air filters that were said to fit nearly every brand of HVAC, but they didn’t fit mine. I bought some air filters from Craigslist that was said to fit mine, but it didn’t. I went to Amazon, and I wanted to try the cheaper fits all brands, but I was wasting my money. The only place I was able to buy an air filter that would fit my HVAC properly, was to buy it from the HVAC company that installed my HVAC. I was able to buy a bulk amount of air filters, which made them even cheaper. I should have thought of this first, because air filters aren’t going to go bad, and they don’t have an expiration date, unless they are in the furnace or air conditioner. I guess it is a lot like my car. I don’t want to go to a Toyota dealer to buy the parts for my Volkswagen, so why would I go to Amazon to buy the air filters for my HVAC. I found out that the air filters were also cheaper when I bought them from my HVAC contractor.