This is a great question. Because we haven’t had a chance to meet you and inspect your unit yet, we can only give you generalities. These are just basic estimates from Consumer Reports. The best thing to do if you’re unsure is simply to give us a call, especially if you could use a reliable HVAC company for your ongoing maintenance needs. The average Electric Furnace lasts roughly 15 years. The average Gas Furnace lasts roughly 18 years. The average Oil Furnace lasts roughly 20 years.