Change it every month, when you pay the gas or electric bill.

Makes it easy to remember.

That can be a good reminder if you actually pay your bill manually. We have everything on auto payment so no bills in the mail.

The installer recommended using the cheapo filters but changing them every month. We always used the more expensive filters but only changed them every 2 or 3 months. We like the heavy duty filters as we get alot of dust and pet hair. So now we are thinking maybe still use those put change them more frequently.

This post was edited by debrak2008 on Fri, Sep 27, 13 at 17:17

Speaking as an ex-HVAC school instructor, and former high-tech clean room worker: The objective of the filter is NOT to clean the air for you (if you need that, get a separate air cleaner), it's to protect the inside from hair and dirt buildup that decreases efficiency.

Cheap filters changed frequently are better than expensive ones changed less often. As soon as you have a layer of dust and pet hair on the filter ... that layer is now your filter. And the air flow goes down and the HVAC efficiency goes down. And the fan works harder.

Wouldn't the better filters protect the furnace more than the cheap ones?