Why should clean coils?
The dust trap, soil, grime, and other troublesome deposits of its cooling coils reduce the heat transfer efficiency of a HVAC system. If the coils are dirty, the airflow of the system becomes blocked and the system requires the Air Handling Unit blower to draw more energy as it tries to move air through the clogged coils. This also creates some additional strain on the condensing system. The additional strain results in the loss of efficient cooling throughout the occupied space and lessens the life of the system components.
Although a coil may look clean on the surface, the majority of the debris could be logged within the coil. What most people see is an accumulation of dust on the fins that are designed to protect the coil.
So, coil cleaning will ensure efficient air flow through the Air Handing Unit to help for optimal system efficiency.