Look what BuildWithRise.com says about Remington Solar attic fans.
Remington Solar
Remington Solar offers 20, 25, and 30-watt solar attic fans. Unlike other products, these solar fans are priced on par with electric attic fans. For example, the 30-watt solar attic fan has the ability to actively cool over 2,200 square feet of attic space and only costs $449. A similarly sized, high-performance electric attic fan would cost the same if not more after factoring in the cost of hiring an electrician. All of Remington Solar´s attic fans also work well for homes that have one or several ridge vents.
https://www.buildwithrise.com/stories/the-scoop-on-solar-attic-fans