One of the easiest and cheapest ways to maintain a gas furnace plus save energy is to change the furnace filter. The filter takes particles of dust and debris out of the air before it goes into the furnace to become warm. A new filter will allow more air to be draw into the furnace and allow for more efficient running of the furnace.
Locate the furnace filter. The filter is usually between the cold air intake and the furnace. Cold air from your house's cold air registers comes into the furnace to become heated air. When the furnace runs, cold air is drawn through the cold air registers and into the furnace passing the filter along the way. Many times the filter compartment will be marked which makes this easier.
Get the right size filter. Each furnace has a correct size filter. The easiest way to find out which size your furnace needs is to look at the old one. It will say on the filter the size. It maybe 18x20x1 or something like this. The manual to the furnace may will have the filter size in it. Heating and air conditioning shops can also help with this. You can purchase furnace filters at all hardware stores.
Changing the filter. Changing the filter is really quite easy. Make sure that the furnace is not running. Pull out the old filter making sure to check the air direction flow on the filter. This tells you the way the air should flow through the filter. Usually this will point into the furnace itself. Replace the filter with the new one.
Mark your calendar that you changed the filter. It's easy to forget when you changed the filter. The filter purchased will dictate the frequency of changing the filter. Some filters are once a month while others are longer. The lower the frequency of changing usually means more cost for the filter. Changing the furnace filter is one of the easiest home maintenance jobs that can be done. Changing the filter can save money and make the quality of air in your home better.