There are so many complex systems and equipment in a home. I have really learned a lot within the past few years because I own three apartment rentals and I am constantly repairing and doing maintenance on the plumbing and lately more often, the hvac systems in these homes. I always stress the importance to my tenants that they needed to replace the air filters in their homes at least every six months. Replacing air filters are so important when it comes to keeping up with a heating and cooling system. Replacing air filters is one of the simplest maintenance things a person can do when it comes to ensuring that a heating and cooling system is efficient in its day to day operations. If someone does not replace the air filter it can lead to a system working in overdrive while it tries to take in air to either cool or heat the air. If an hvac system is constantly working hard to do simple functions, eventually it’s going to break down. Just by having a dirty air filter that is not replaced, it can cause other equipment within the hvac system to become faulty and eventually stop working. To ensure that the air filters are being replaced within the houses that I own, I leave a maintenance log near the heating cooling system and I actually will write down the dates of when the hvac air filter should be replaced. My tenants probably think I am being anal about it but I do not want to have to spend money on a completely broken down heating and cooling system. This would cost me thousands of dollars!