[derobert]

Dehumidifiers are ACs, just with the condenser indoors and exhausting heat back into the cooled air stream (so heating the room overall).

A particular dehumidifier can (of course) be more or less efficient than a particular AC system. But it's probably more efficient, given similar technology, if you want a drier, warmer room.

Hardly ever want that warmer room bit during the Southeast US humid season. So you'd wind up running the AC too, to exhaust the excess heat (including the extra heat from the dehumidifier).

[occz]

I'm specifically only thinking about the case where you run an AC while not at home. By all means, run your AC if you are at home and need to manage the temperature.