I love all these experts. I was in the business for over two decades. First: many sizes of solar attic fans
2-26% Federal Solar tax credit
3-Air Vent makes the only reliable ridge vent. Go to their web site to learn why standard ridge vents seldom work as designed
4-principle of attic ventilation is to bring in the cool air from the soffit vents to displace the hot air in the attic through the fan
5-the best location for a roof fan, be it electric or solar is at the peak of the roof which means blocking the ridge caps to prevent negative air flow.
6-even in the colder months you still need to vent your attic. Electric fans have T-Stats while, unless you live in Arizona, Solar fans run year round.
7-Solar fans use ball bearings and generally have a 20 to 25 year warranty. Check the warranty on electric fans as well as the motor.
Hope this helps.