There is a chart out in the market place that shows what you save by reducing the attic temp each degree. Its pretty amazing. The attic fan with thermo settings is great to maintain a stable temp. But, you need to have the appropriate amount of these on your roof based on the size of the attic. These should also work in conjunction with soffet vents, eaves and other. You want a nice smooth draw and movement of air.
when I think about this if your reduce the time the HVAC comes on with all the componets needed to cool air, the fan, the blower, the compressor and so on, that is allot of energy. The attic fan is one simple reverse fan.
The attic fan like I said before is a part of a compete system. It cannot work alone. Its a team thing. It goes hand in hand with good insulation, good soffet vents, good insulation around the ducts, replacing the old duct tape if you have that, changing the filters each month, making sure the compressor and vents are not obstructed by plants and have good ventilation, making sure that the system is charged up and running properly.
Not one of these will work alone.
I therefore would have to disagree on the premise that an attic fan consumes more energy in running than it saves in reducing heat in the attic.