Coil cleaner is a specialized chemical solution used to remove dirt, dust, grease, and biological growth like mold and algae from the evaporator and condenser coils of an air conditioning unit. Over time, this buildup acts as an insulating blanket, forcing the system to work harder, reducing its cooling capacity, increasing energy consumption, and leading to higher utility bills and potential premature failure. Using a coil cleaner is a critical part of routine AC maintenance, as it restores airflow and heat transfer efficiency. It is important to choose the right type of cleaner—typically either a mild, no-rinse foam for light dirt on evaporator coils indoors, or a stronger, alkaline-based cleaner that requires rinsing for heavily soiled outdoor condenser coils. For safety and to avoid damage, the system should be powered off, and protective gloves and eyewear should be worn during application. While coil cleaning can be a do-it-yourself task for accessible units, hiring a professional HVAC technician is recommended for a thorough, deep clean, especially for complex or hard-to-reach systems, as part of an annual maintenance service.