The answer to 'when to replace central air' is that central air conditioning units typically last 15-20 years with proper maintenance. However, there are several factors that can impact the lifespan of your system, including the unit's efficiency, the climate where you live, and how well you've maintained it over the years.
As your central air system ages, you may notice a decline in cooling performance, higher energy bills, and more frequent breakdowns. If your system is over 15 years old and requires frequent repairs, it's generally a good idea to consider replacing it with a newer, more energy-efficient model. This can help you save money on utility costs and reduce your environmental impact in the long run.