We recommend that the device not be used below about 40 F and 30% humidity. If you have those conditions 8 months out of the year, it certainly pays. If you are in a marginal zone or have humidity but little rain, any water you can get is a good thing.

These devices have the potential to drive back deserts by creating microclimates and grasslands, then slowly expanding in from the margins of the deserts. Remember that the entire Southern shore of the Mediterranean was once the bread basket of the Roman empire.

No one answer works for every place all of the time. I would not recommend these devices for most of Nevada or Arizona. If, however, there is no significant rainfall and I were a subsistence farmer, I'd rather extract some moisture than have none.