I have not fully figured out the payback, but the tax lady said there is a 30% payback with no cap up thru 2016 on wind and solar here in the USA.  She said that it would not pay past 0 tax paid in, being if my tax liability is low I would not get the full 30%.  But if my math is even near correct, it could mean around $1200 - $1800 more in refund the next few years and help lower my electric bill.  I think with a 60' mast, where I live, I could use it to at least half of its potential and maybe even put back to the grid once in a while.  And fully get the neighbors talking.  I am not so dumb this year with the OWB.  Fuel oil and propane skyrocketed, and I still have 45% of my original tank from August 2010.  
I would like to move on something before the regulators put a law in place to stop me from saving MY money.  We all hear the stories of the anti-OWB movement, I think the windmill will be next because it is eye pollution