AFUE stands for Annual Fuel Utilization Efficiency and it measures the
efficiency of a gas furnace. The higher the percentage, the more efficient your machine. AFUE is a ratio: Annual heat output of a furnace or boiler v.s. total annual fossil fuel energy consumed by the furnace or boiler. If your rating is 80 percent than 80 percent of the energy consumed is being used to heat your home and the other 20 percent escapes as exhaust. Consumer Reports says that a 90 percent AFUE can cost about $1,000 more than a similar sized 80 percent AFUE, but “that additional cost can generally be recouped in lower fuel bills over the lifetime of the furnace.”
