re: Do you buy the one month air filter or the 3 month air filter?

quote:

---

Change it when it gets dirty.

---

+1

Stuff like this doesn't work on a calendar, it's about when it gets dirty. And that depends on individual situation.

Check it once a month until you get a feel for it. Replace when dirty.

And as others said, high high MERV is going to restrict air flow - that might cause problems and/or lower the efficiency. I go cheap, good enough for me.