How often should you change the filter on your heating and AC unit?

Summary

It all depends where you live -- what the air pollution levels are in your area, and what kinds of pollutants you have inside your house.

One should at least inspect the filter every 30 days and change it if necessary. If clean, check at least every 45 days. If a central air conditioning and heating system is used regularly, the filter should be changed at least once a year.

A filter change costs a couple of dollars, but it is the most important thing you can do to avoid problems later. if you let it go, the blower motor works harder, shortening its life or your evaporator coil could become your filter, blocking airflow and causing it to start icing up; this can cost hundreds of dollars to remedy.

If you smoke in your house, have inside pets, or a large amount of traffic in the house, check the filter once a week. The outside environment should be considered, since dust storms and high pollution areas do affect the filter as well.