Solar Powered Attic Fans ; good investment and reliable ???

Proper passive venting will probably work better and be more dependable.

I've never seen much positive here about solar powered fans.

Solar hot water is often a good deal and passive solar heating helps.

Solar-electric anything is a bad investment.

Check here for the skinny on solar fans (but it's a competitive site, so take with a grain of salt)

One calculation you could make is to figure out how long an equivalent fan would have to run to consume the $217-70=3D $147 worth of electricity. That is what you are paying for up front. I'll bet it's quite a long time because the solar fans are not very powerful. Balance that against the probability that the solar fan lasts that long. I'd also bet the $70 regular fan moves a lot more air.

In general, I believe passive attic venting is best, ie good soffit venting together with a ridge vent.

Hi, What is the rating and spec.?

Passive venting does nothing. The regular fan with a thermostat will be far better

I don't know where you got that notion, but it's wrong. If you have soffit vents and a ridge vent done properly, it will be far more effective than any fan you install. It's not even close.

Keep kidding yourself, Hot humid air will go nowhere without help

Didn't they have schools where you grew up? Seriously.

OTOH, I think there's room for both, at least here in Texas, where convection alone is strapped to keep up.