If you’ve been looking at various types of furnaces, you’ve probably noticed that they all have what’s referred to as an AFUE rating. This number is a reflection of the energy efficiency of the furnace, and will typically be between 80% and 98%. The higher the number, the more energy efficient the furnace is.
Although you should always take the AFUE rating into account when you’re purchasing a furnace, that doesn’t mean that you should necessarily go with the model that has the highest efficiency rating. Depending on your heating needs, an 80% AFUE furnace may be able to get the job done just fine without forcing you to incur the greater costs that come with the higher efficiency models.