What is the efficiency of a 20-year old air conditioner?

Older HVAC units tend to be less efficient than newer models, and as they age, wear and tear further reduces their efficiency. While a replacement HVAC unit is a significant investment in your home, it can make more financial sense if it saves you money on repairs and utilities over time. Most 20-year-old HVAC systems are at the end of their lifespan, and if they become increasingly expensive to maintain and operate, it's probably a good time to consider replacing them. Since the average age range of an HVAC system is 15 to 25 years, you may be wondering how efficient your 20-year-old system is and if it's time to consider replacing it.