Even with 35% in fuel savings, it might be a poor economical choice to replace that furnace. The new furnace might only last 15-20 years and have to be replaced yet again - and new furnace installations will only get more expensive with time. He would be better off to accept the low efficiency of the furnace, which will last, essentially, forever, and put money into making his home more efficient in other ways. Jim / Howard, Absolutely, I agree. Better to spend the money on improving the house's efficiency, thereby resulting in a lower fuel bill each month. You guys are right, it's a simple, reliable furnace that should run for many more years.