Using an incorrectly sized air filter won't necessarily damage your air conditioning system, but it can have an impact on its efficiency. If the filter is too thick or too thin, it can cause air to bypass the filter and return to indoor air, leading to higher energy bills. It's also important to consider the MERV rating of the filter, as a higher rating can improve air quality. It's a common misconception that using an air filter with a higher MERV rating is the best option.
However, if there is any resistance to airflow caused by the use of a filter that is not the correct size, it can cause unnecessary stress on the air conditioning unit itself, which could damage the system equipment and increase your energy bills. Poorly sized or incorrectly installed filter frames can cause air leaks, significantly reducing filter efficiency. When you're shopping for an air filter, it's important to keep in mind the size of your HVAC system. You're shopping at your local home improvement store and all of a sudden, you remember that you need to buy a new air filter. To put that into perspective, a 1-inch air filter may need to be changed every month, while a 4-inch air filter can last up to six months.
Reducing the thickness by one inch shouldn't be a big problem; for example, you should be able to use a 4-inch filter instead of a 5-inch filter. If you try to use a 4-inch-thick air filter in a system that's made for a 1-inch-thick filter, the efficiency will actually worsen. A 1-inch filter with less surface space will clog up fairly quickly and will need to be replaced much sooner than a coarser filter. If you opt for a smaller filter or nothing at all, at least do something like tape or glue a piece of cardboard filling to the filter to get the correct size. So, if it fits your oven, then a 4-inch air filter is better than a 1-inch air filter to improve air quality. It's important to make sure that you purchase an appropriately sized air filter for your HVAC system in order to maximize efficiency and reduce energy costs.
