The higher your new furnace’s AFUE rating the better your energy efficiency will be. The minimum AFUE rating you will find on the top brands will be a 78% rating. A mid-efficiency furnace will have an 80% to 85% AFUE rating, while a high energy efficient unit can get up to 90% to 97% AFUE rating.
While some homeowners prefer to install a furnace with standard AFUE rating to save money on initial furnace replacement costs, it is often a good idea to opt for higher energy efficient brands if your budget allows.