Your furnace can last a long time if it’s properly taken care of — it’s not unheard of for a furnace to last as long as 15 to 20 years in some cases. However, there are certain signs that indicate it may be time to have your furnace replaced. These include the following:

• The constant need for repairs – If your furnace is constantly having problems that need to be repaired, then it’s a sign that your furnace is never going to be in tip-top condition. Even if those repairs are minor, the costs of small repairs will add up eventually.
• High repair costs – Your furnace may have been functioning in perfect condition for years, but if it’s suddenly experienced a problem that is going to require a large repair cost, replacement might be worth considering. The general rule of thumb is that if the cost of repair is going to cost more than half what it would cost to install a new furnace, you should just go with a replacement.
• Reaching the end of its lifespan – Once your furnace passes the 10-year mark, it’s more likely to experience issues as a result of general wear and tear. At this point, newer models are going to be much more efficient and effective as well.
• Improperly sized – A furnace that wasn’t properly sized to meet the needs of your household is going to have all kinds of issues, especially where efficiency is concerned. If it’s too small, it won’t be able to handle your household needs, if it’s too big, it will waste energy.
• High heating costs – If your heating costs have gone up significantly, it means something is causing your furnace to run inefficiently. There’s a good chance that you may need to upgrade your furnace if this is the case.