MERV stands for minimum efficiency reporting value and it describes how effective an air filter is at removing dust and other contaminants. The higher the MERV rating, the more effective the filter is. The carbon-coated furnace filter we use in our HVAC system has a MERV 16 rating — the highest our HVAC unit can support. Keep in mind that the higher the MERV rating is, the lower the airflow is. So check out the specifications of your air conditioning unit before you replace the existing filter with a more effective one.