For several reasons:

1.Dirty air filters represent the #1 cause of system breakdown. A dirty air filter restricts air flow into your HVAC system’s air handler, placing additional strain on the air handler fan motor. Over time it can burn out the motor, cause your system to overheat, and ultimately fail. Filter replacement is essential to extending the life of one of the biggest financial investments in your home. 

2.A dirty air filter consumes more energy, by making your fan motor work harder. One of the easiest and quickest ways to reduce your energy bill is to replace your air filter. 

3.A dirty air filter reduces the air quality in your home, aggravating allergies and asthma (particularly in children and the elderly). Change your filter regularly to protect your family’s health. 

4.A dirty air filter makes the rest of your heating and air-conditioning systems and ducts get dirty faster. This leads to costly air duct cleaning expenses or the need to replace your unit(s) sooner than you expected.

Electronic air cleaners do not require filter media replacement, but instead require cleaning of the cells in inside the unit. Clean every 3 months to keep these units running smoothly.