What does a furnace's AFUE rating measure?

The AFUE rating stands for Annual Fuel Utilization Efficiency, which is a crucial metric used to evaluate the efficiency of heating appliances like furnaces. This rating expresses the percentage of the fuel energy that is converted into usable heat over the course of a year. An AFUE rating of, say, 90% means that 90% of the fuel consumed is converted into heat for the home, while the remaining 10% is lost through exhaust or other inefficiencies.

Understanding AFUE ratings is important for consumers who want to select energy-efficient heating systems, as higher AFUE ratings typically indicate lower energy costs and greater environmental benefits by reducing fuel consumption. Knowing what AFUE represents helps homeowners make informed decisions when purchasing a furnace, ensuring they select a system that meets their heating needs while being mindful of energy efficiency.

The other options, while they contain elements related to fuel utilization, do not accurately define the AFUE measurement, which specifically refers to annual performance rather than average or functional assessments.