[turbo6bar]

I have been thinking about one or more of these fans for an attic gable. The prices, however, are outrageous. An AC powered fan is less than $100. The solar powered units are $400-600 for similar output. Even with a Federal tax credit, that's still a huge premium. It would take decades to recoup the extra expense. The only way I can see making it work is a DIY solution.

I've noticed fan outputs vary wildly. The sellers of solar fans claim 800-1000 CFM output with only 25 watts. On the other hand, if I bought a set of SPAL electric radiator fans, the electrical need is 12 amps for 1200-1400 CFM. I know fan output is dependent on pressure head, so how do I choose the right match? Naturally, I want the highest output per watt, so the solar panels do not have to be huge and expensive. jurgen