A.C. Filter Ratings

MERV

• The reporting system used to describe the efficiency of air conditioner and furnace filters is called the Minimum Efficiency Reporting Value system, or MERV. This system was developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers to provide consumers with a means of comparing filters for their heating and air conditioning units. The higher the MERV rating a filter has, the smaller the particulate it is capable of stopping. MERV ratings for residential use range from 1 to 12.

Applications

• Disposable residential air conditioner filters typically have a MERV of 1 through 4. You must replace these filters on a regular basis, typically once per month or more frequently under high dust conditions. Pleated filters, which may be disposable, have MERV values of 5 through 8 and may be twice as efficient as disposable filters. High-efficiency filters, such as extended surface pocket filters, can reach efficiency levels of up to 98 percent, according to the Commercial Filter Service website.

Pressure Drop

• MERV is not the only rating that's important to consider when selecting an air conditioner filter. You should also look at the pressure drop rating. Pressure drop, sometimes referred to as filter resistance, measures the filter's impact on airflow through the air conditioning system. Filters that offer a low pressure drop allow the unit to operate more efficiently than filters with a high pressure drop. The pressure drop rating tends to increase as a filter becomes clogged with particulates.

Considerations

• High-efficiency air conditioner filters can trap tiny particles of dust and debris, but they can also restrict the airflow necessary for your air conditioning unit to operate in a cost-effective manner. Since different types of air conditioners have different requirements, you should consult your owner's manual before changing to a filter with a different MERV rating.