What is a common indicator that air filters need replacement?

Increased energy bills without any other reason is a common indicator that air filters need replacement because clogged or dirty filters restrict airflow throughout the HVAC system. When filters are blocked, the system has to work harder to circulate air, leading to increased energy consumption. This additional workload can cause energy bills to rise noticeably over time.

On the other hand, improved airflow from vents would typically suggest that the filters are clean and functioning well, while stronger odors in the building could be a result of various issues unrelated to filter cleanliness, such as mold or other contaminants. Colder air production may indicate the system is operating effectively but does not directly address the condition of the air filters. Therefore, noticing a rise in energy costs is a significant and common signal that indicates a need for filter replacement.