Recently, I've been wondering why we use exhaust fans in bathrooms and not dehumidifiers. I might be way off base here, but it seems like taking conditioned air that's a little moist and dumping it outside and replacing it with drier unconditioned air would be less efficient than just removing the moisture from the already-conditioned air.

I imagine it isn't one of those things where it's "always cheaper to do X", but there's probably a break-even point. Does anyone know how to do the math to draw that chart?

Think about some of the other things that happen in the bathroom, and ask yourself whether you'd want that air recirculating in your house.

too dry air ain't very good for your "mucous" membranes (nose, throat, eyes etc). You want to be sicker just to save few bucks for heating? If poor, I guess it's the only option, but otherwise having heated place is same "luxury" as say buying a cheap & good coffee in the morning instead of doing it yourself...