You've heard the old adage, "Out of sight, out of mind." It applies to many things, including home HVAC. Though heating and cooling appliances are very easy to overlook, the conscientious homeowner cleans or replaces the equipment filters regularly. There are two reasons to do so. One is that HVAC filters directly impact indoor quality. The other is that dirty filters lead to higher energy bills, so filters kept clean can contribute considerable savings.