The answer to 'average cost for air filter' is that the typical cost for a standard HVAC air filter ranges from $5 to $25, depending on several factors. The size, quality, and MERV rating of the filter can all impact the price. Higher-end filters with better filtration capabilities tend to be on the higher end of that range.
It's important to replace air filters regularly, typically every 1-3 months, to maintain the efficiency and performance of your HVAC system. The cost of replacement filters is generally low compared to the potential savings from improved system operation and energy efficiency. Always consult a local HVAC professional to determine the right filter for your specific system and needs.