If your furnace is 15 years old or more, now might be the right time to exchange it for a more efficient model.
The obvious reason is to reduce your energy costs, keeping in mind that winter is on its way. Data from the U.S. Department of Energy show that if your current furnace has an AFUE (Annual Fuel Utilization Efficiency) rating of 50 percent, one with 90 percent will save you $44.24 a year on every $100 you now spend on fuel costs.
In addition, upgrading your furnace or boiler from 56 percent to 90 percent efficiency in an average cold-climate house will save 1.5 tons of carbon dioxide emissions each year if you heat with gas, 2.5 tons if you heat with oil.