Periodically replacing your air filter will significantly improve your heating and cooling system's performance. When the filter is dirty, the fan uses more energy to force the air through. When the filter gets too clogged, the whole system can shut down --triggering the need for professional services that could cost hundreds or even thousands of dollars.
Experts recommend that you change the filter every three months. It only costs a couple of bucks, and pays for itself almost immediately. The filter is normally located in a pull-out tray either in the main unit or in the ductwork near the unit. Most furnaces use disposable paper filters, but some filters can be cleaned and reused.
Also, regularly clean registers where air is supplied and returned throughout the rooms in your house, while clearing obstructions from any baseboards, radiators, or vents. Not only will you save money and help avoid costly repair bills, you'll be breathing cleaner, healthier air, too.