Change your furnace filter! If your furnace runs efficiently it will save you money. To run efficiently a furnace needs to be able to draw air through the filter. Furnaces have a filter at the cold air return and it’s easy to change this yourself. As the dusty air gets sucked in through the return the filter clogs. The most efficient solution is to mark your calendar to change your filter and put a new filter in. I try to change ours every three months, but ideally you could change your filter as often as each month.