Typically, a residential furnace will last between 15 and 20 years. If your unit is reaching this age, it’s time to start planning (and saving!) for a replacement, even if it’s not having any problems. If your furnace needs frequent repairs, regardless of age, replacement is a wise option. HVAC repairs can become quite expensive if you need them repeatedly, and they often stem from underlying damage that will require more costly repairs in the future. It makes financial sense to replace an old furnace, even if it’s in good operating condition. A more modern, energy-efficient unit may justify its cost with lower heating bills. Conversely, if your heating habits have been consistent but your energy bills are rising, this may be a sign that your furnace is wearing out and having to work harder than it used to.