Generally speaking, you can expect about 15 years of use from your furnace or air conditioner. That figure varies depending on operating conditions and equipment type. Meanwhile, equipment that isn’t properly cleaned and maintained can wear out much more quickly. If your furnace or air conditioner is older than 15 years but still running, it may still make financial sense to consider a replacement. HVAC equipment is significantly more energy-efficient than it used to be, and the difference in fuel consumption could pay for your investment in just a few years.