If you have a dirty air filter, it can cause low airflow and make your HVAC system work harder than necessary.
Yes, pleated air filters do restrict airflow to your HVAC system, but all air filters will restrict airflow to some extent. What you should focus on is finding the right filter for your unit and overall system to reduce the amount of contaminants in the air as much as possible. Generally, a filter with a higher MERV rating will reduce airflow, but there are other factors to consider such as the size of the filter and the type of fan motor in your HVAC system.
Most modern HVAC systems have no problem working with higher MERV filters, so millions of homeowners depend on them. The main risk of high-efficiency air filters comes from not changing them regularly. If you keep up with changing filters, you are unlikely to experience any filter-related issues with your HVAC system. Electrostatically charged filters work well for about a week or two, but once the surface is “covered” by particles, the electrostatic benefit disappears.
This includes electric air purifiers too. Air conditioners can turn off if fine filters restrict airflow too much. The air conditioner is also stressed by a dirty filter that slows down airflow, causing the system to work harder. In addition, your system may not be able to provide enough heating or cooling to the home or just one or two rooms become uncomfortable.
High MERV pleated filters capture a large amount of contaminants, but they also restrict air movement to the blower or oven. As a result, the fan has to work harder to heat and cool your home, reducing efficiency. If you have a return grid filter system or if your ductwork can only accommodate one filter in the chamber, avoid high MERV 1 filters (above MERV 8 is quite restrictive). Some technicians anticipate that people will forget to change their filters, so regular use of low-efficiency filters could help minimize damage to a neglected HVAC.
For example, Second Nature's Essential filter is approximately 450% more effective at trapping particles than a cheap, low-efficiency fiberglass filter, but its resistance to airflow is only 20% higher, a marginal difference. It is recommended to change filters in this category every two to four weeks, which may be difficult for some to maintain. You can clearly see how the air filter reduces the total external static pressure by increasing the pressure drop. The boiler blower or fan will not be able to move enough air through the filter without assistance, so HEPA filters are usually installed as part of a system with an included fan. Low-efficiency filters are generally within MERV 1-4 and high-efficiency filters are MERV 13 and later.