Don’t use pleated air filters! You wouldn’t drive your car towing a hundred pound block around—don’t do that to your furnace! Overly restrictive filters slow airflow through your furnace—usually well below what the furnace requires for efficient operation. Reduced airflow leads to higher energy bills and durability issues, (overheating the furnace, over cooling the A/C coil, overworking the blower motor). Have your furnace’s airflow tested next time you have it serviced! A/C requires 400 cfm per ton for maximum efficiency. Cheap filters don’t restrict airflow and can be sprayed with a treatment to improve dirt collection.