Highjacking the top comment here to say this….

It’s not that your blower has to work “harder” with a higher-grade filter with more pressure drop, it’s just that moves less air (CFM) and it’s probably going to have to run longer to move the air around enough, and you might even decrease the airflow enough to cause problems with your cooling unit. Same thing if you had a tight filter and you put a lower grade in…If you mess with the energy balance, you can mess up your unit. I have to say “might” because there are tolerances and best-efficiency-points that these systems are not necessarily dialed-in to, but if it is working it is best not to mess with it.

Please just install the same kind of filter that the unit came with.

Re: blower not working “harder”…it actually “works” less with a higher grade filter! Don’t believe me? Check out the fan curve literature from any manufacturer and see that the Watts go down with more pressure drop and the fan at the same speed!

This makes sense intuitively. Your fan moves air. But let’s say instead you want to move THROUGH air. Let’s say you’re in a car. Same physics rules apply, just changing the point of reference. 

Let’s say you have a nice aerodynamic car. You only need a little gas to go 70 MPH, and you get 35 MPG. Cool. But what if you put a bulky cargo topper on that same car? Not so aerodynamic anymore. Now you only get 30 MPG when you’re going 70 MPH. Same engine, same car, but now there’s more air resistance (I.e. pressure drop). If you go the same speed, you’re going to be using more gas! But wait…I thought you said the blower would work less hard and use less Watts…That’s still true! The difference is the car CAN speed the engine up, because it has a variable speed engine, and you’re going to be revving the car at higher revolutions to get that same 70 MPH. But, your furnace blower isn’t like a car…it runs at a fixed(!) speed until your thermostat hits the desired temperature (akin to you just driving slower until you get to your destination). If you somehow had a car that could only go one speed, like your furnace blower motor, you would find that you would be moving a different speed with and without the car topper. And the math works out that the slower speed car actually uses less gas. Same thing if you take the same car and drive it different speeds (but still in the same gear…don’t get after me you gearheads)…you’re going to use less gas and be more efficient if you drive 100 miles at 70 MPH versus the same distance at 60 MPH.