If your system only fits a 1- or 2-inch filter, a high MERV rating could be detrimental. A 1-inch filter with less surface area will clog up quickly and need to be replaced more often than a coarser filter. The higher the MERV rating, the better the filter will be at blocking particulates. This means that a 1-inch filter with a high MERV rating can work just as well as a 2-inch filter with the same rating. Filters only work if air has to pass through them.
The filter has air resistance and a gap does not, so if you leave a gap of 1, an excessive amount of air will flow through the hole, which will further worsen the situation. When you want to improve air quality through better air filtration, but don't want the expense of modifying your equipment, a 1-inch 13 MERV filter can do the job. Particularly vulnerable parts include the air handler or oven blower motor that works overtime to push and draw air through the dirty filter and the heat pump or air conditioning compressor responsible for circulating the refrigerant between the outdoor and indoor units.1-inch pleated air filters have higher MERV ratings for one simple reason: they have more surface area to trap particulates. The smaller filter area will behave like a filter that is already partially dirty, but you can use it temporarily.
What had changed was that technology recommended that you only use filters at home and eliminate the return of air handlers. It's a technical way of saying “how many particles and how many small particles it filters out of the air you breathe. You would have to replace filter 1 twice as much as a filter 2 and risk damaging the air handler (fan motor) by increasing the resistance you have to push against. Bottom of the line filters don't meet your needs, as you're using a cheap filter to keep big things out of a pleated filter.
The reasons for replacing filters in central air systems is because they become too restrictive on airflow (CFM) or start to not work as well by letting in the same things they are trying to filter if they aren't replaced over time. Assuming that it is a PSC motor in your unit, the actual amperage draw of the motor will be reduced with a reduction in CFM (the net effect of a reduction in return air CFM will cause your central air unit to wear and tear more, as the motor will have to spin more RPM to move less air throughout the house putting more wear of the brushes (if you have them) and the bearings, and the use, in total, of more power because it lasts longer. So, if you choose a filter 1 with a high MERV rating, you'll have to change it every month or two when the oven, heat pump, or air conditioner is heavily used. Multistage filtering is not a bad idea, and it is done in many environments (especially commercially) for the same reason you asked, carrying only pre-filtered air with what is left to the more expensive step filter. I added that filter in the odor unit, which caused the air handler to work longer and, in this case, more efficient.
There is another approach that doesn't require multiple filters or replacing them, and that is to use a permanent filter. If you can't find a standard size filter within that parameter, you'll need to order a custom-sized air filter.
