Living in Texas myself, there is a formula that any of the energy providers especially TXU provides that will show you for every degree you cool the attic in the summer will require less strain on the HVAC unit and be cheaper for you also.
So, I agree hardily that the energy to run the units is definately offset with the lower strain and energy consumption of the unit.
many people do not realize how many wind driven twirly birds a home needs to make these work properly. Thermo set and activated fans do work and I would recommend that you replace them. Consider up grading the CFU's that they remove also. Do not set the thermostat too low for the attic. 95 degrees is good.