An Aerostar furnace air filter helps keep your HVAC unit working efficiently by removing dirt and reducing strain on the motor. When your unit runs properly, it consumes less energy, requires less maintenance and will have a longer life. These factors will have an impact on your utility bill and maintenance costs. It is recommended that you change the filter every 60 to 90 days during normal times of year but increase frequency to 30 days during peak summer and winter months when your unit is working the hardest.