Filters on your HVAC system are there to help improve the indoor air quality and to protect the air handler. A dirty a/c filter will lead to increased operating costs and poor cooling.
Dirty A/C filters can -
1. reduce air flow out of the registers
2. reduce air that the air handler unit needs to operate properly- choking the unit and using more electricity
3. cause dirt build-up inside the duct system.This can lead to mold or allergen problems in a building and to the need for more costly duct cleaning or replacement
4. let dirt insulate the cooling coil itself, reducing the effectiveness of the coils and could lead to costly repairs
5. lead to ice build-up on the cooling coil and reduce or totally block air flow in the system
6. eventually permit dirt to go around the filter where it soils and blocks the blower fan itself, leading to more costly repairs.
Nothing good happens when dirty a/c filters are left unattended.The filters on an air conditioning or hot air heating system should be changed regularly.
Remember that you need to protect the most expensive investment in your home with regular checkups (2 a year) and regular changing of the filters before they are completely full!