The answer to 'when to replace evaporator coil' is that the evaporator coil should generally be replaced every 10-15 years, or sooner if it becomes damaged or corroded. The evaporator coil is a critical component of your HVAC system, responsible for absorbing heat from the air inside your home. Over time, the coil can become less efficient, leading to increased energy costs and reduced cooling performance.
Factors that can impact the lifespan of an evaporator coil include the quality of the coil, the environment it's installed in (e.g., coastal areas with high humidity), and how well the HVAC system has been maintained. Regular maintenance, such as cleaning the coil and ensuring proper airflow, can help extend the coil's lifespan. However, even with proper care, the coil will eventually need to be replaced to keep your HVAC system running efficiently.