This question is asked by many of my clients who are first time home buyers. It probably should be asked by many seasoned home owners as well.
There are a hundred variables to the answer, like how many people and pets live in your house, how dusty is it around your home, and most important, what kind of filter do you have? But a simple rule of thumb is a basic 1” filter should be changed every 3 to 6 months at least, and the thicker 4” media filters should be changed at least once a year.
Keep in mind that dust and dirt is everywhere, and that is what clogs the filter and reduces air flow. Dirty filters cause your furnace to work harder, use more energy, and push around less healthy air. So use those timeframes as a guide, and when you first buy that new home get in the habit of checking your filter every few months to see how it’s coming along so you can develop a maintenance routine that works for you.
Your home inspector DID show you how to change the air filter right?