An HVAC coil moves heat between the system and the surrounding air. Deposits on the heat-transfer surface and restrictions to airflow can make that job harder. That is why inspection and cleaning belong in the maintenance plan.
Preparation comes before treatment.
Inspect the coil, identify the material and any protective finish, and select a compatible cleaning process. Organic residue and mineral buildup may require different products. Applying a treatment over remaining deposits is not the same as treating a properly prepared surface.
Measure the system you actually have.
A fair evaluation looks beyond a single power reading. Load, weather, airflow, operating settings, and equipment condition influence results. Establish comparable baseline and follow-up conditions before attributing an energy change to any one intervention.