Any dust that passes through the filter ends up back in your living space and can be very irritating to allergy sufferers and anyone else who is sensitive to dust.
The filter also prevents the evaporator coil from becoming clogged with dust and reducing the efficiency of the equipment.
This evaporator coil is very similar to the radiator in a car. Like your car radiator, it will not be able to do its job without proper airflow. The reason I’m comparing it to a car radiator is because most of us know what a radiator does, but an evaporator coil works to cool air as it passes through.
It could take months or even years for dust to accumulate in the fins of the evaporator coil; it can even form a layer of dust on the fins.
If your air conditioner is serviced regularly the technician will check this and tell you when it needs to be cleaned, if this is not done it will lead to expensive repairs.
So the benefits of an efficient air conditioner filter would not only be cleaner air, but save you money because the air conditioning will perform at a higher efficiency.