Our central air furnace/cooler (Lennox Elite CH33-42B-2F) takes 4" filters. They can work out quite expensive, so my question is, will the system work just as well if I change to standard 1" filters, or is there something else in the equation that I'm not considering? (fitment isn't an issue - I'd use a 3" blanking frame)
I favor the thick filter. We have a SpaceGuard filter unit with pleated paper filters (Aprilaire No 201) and I think this yields a superior filtration without excessive restriction. I change it once a year.
The thicker filter is better if it is the right one for your unit, i.e., it is not too restrictive. Some people put a filter on which is too restrictive and this puts excessive load on the circulation fan motor. Our system has been in service for 25 years with the original blower motor.
The fan on the condensing unit quit last year and our HVAC service replaced it.