You may not know it, but keeping your furnace and A/C clean can help reduce heating and cooling costs. Here are some dirty little secrets you should know:

“A build-up of .042 inches of dirt on heating or cooling coils can result in a decrease in efficiency of 21%.” (EPA) Environmental Protection Agency.
“Clean systems restore capacity and lessen running time.” (LCES) Louisiana Cooperative Extensions Service.
“Most commercially purchased fiberglass filters are only 7% efficient in stopping dirt, dust, pollen, etc. from passing through it.” (ASHRAE) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
“Nine out of 10 system failures are caused by dirt and dust.” (LCES) Louisiana Cooperative Extensions Service.
There are two coils in the system; an indoor coil (sits over the furnace in the ductwork – you cant see it) and an outdoor coil. To keep your coils clean, call a professional technician for a tune-up at least once a year for each system.