Question: what is the difference between an 80 efficient furnace and a 90 efficient furnace?
Answer: Therefore, with an 80% efficiency furnace you are only receiving 80% of the heat that you pay for. With a 90% efficiency furnace you are receiving 90%. ... All in all, the major difference between the two is how the 90% efficiency furnace really can save more money and efficiency than the 80% efficiency furnace.