Understanding natural gas furnace efficiency and costs is essential for homeowners planning an upgrade or replacement. This guide explains AFUE ratings and how they impact energy savings, along with proper BTU sizing to ensure efficient heating without wasted fuel. It also covers average installation costs, ongoing maintenance schedules, and common warning signs that indicate a furnace may need repair or replacement. By breaking down technical details into clear, practical insights, homeowners can better evaluate performance, budget expectations, and long-term efficiency. Knowing how to choose the right furnace helps improve comfort, reduce energy bills, and extend system lifespan.