This is a great question! We want to stress the importance of changing your filter frequently when your furnace or air handler is in use. You may or may not have air conditioning in your home – you would not be changing your filter in the summer if you don’t.
It is so simple to maintain your filter, and it only takes seconds to swap it for a new one.
At the very least, check it every 30-45 days. If it is looking dirty, replace it. At bare minimum, replace it every 2 months.
If you have a high efficient furnace and you neglect your filter maintenance, you may plug up the secondary side of your furnace heat exchanger. The high efficient furnaces are much less forgiving than the older mid-efficient furnaces. This can cause severe damage to your heat exchanger from over heating.
There is a myth that a plugged filter is harder on your furnace motor, but actually the amperage draw will be lower with less air flow. The motor windings will get dirty and shorten the life expectancy of your motor if your ducts are dirty and filter is passing dirt and dust through it.
If you have air conditioning, your evaporator coil in your plenum also runs the risk of being plugged. Depending how your evaporator coil is installed, cleaning it may involve completely removing it from the ductwork – which can get costly.