Q. Your neighbor lives in a 2000-square-foot older home heated by natural gas. The current gas heater was installed in the early 1970's also has efficiency (Annual Fuel Utilization Efficiency or AFUE) of 65%. It is time to replace the furnace also your neighbor is trying to decide between a conventional furnace with an AFUE of 80% which costs $2,200 also a high-efficiency furnace with an AFUE of 95% which costs $3,600. Your neighbor has offered to pay you $100 if you assist in making the appropriate decision. Considering the weather data, typical heating loads also the price of natural gas in your area; make a recommendation to your neighbor based on convincing economic analysis.