How often should I change my furnace filter?
This is the one thing that an owner can do to increase the life and efficiency of a furnace and A/C system. The filter is the number one culprit of causing maintenance problems and system failures. It is recommended that the furnace filter be changed once a month. However, if you remove the filter and hold it up to a white light and it doesn’t look opaque then you can change it every 3 months.