I recently updated our Wind Turbine Power Calculator to include the 30% tax credit incentive. This definitely helps to drop the period of payback in years and increases your ROI, but I am finding overall that unless your average wind speed is 14mph or higher and you are paying 16 cents or more per kwh, it does not pay to install most residential wind turbine systems.
One factor that might help is where utility companies or states provide additional rebates or tax incentives to further reduce the cost of the wind turbine purchase and installation, but since this varies so widely from state to state I haven't chosen to track such items, however a good list of these possibilities is found at http://www.dsireusa.org/summarytables/finre.cfm
I'm not giving up on wind, but I am finding it increasingly difficult to even find out who certain distributors are so that I could determine if a new design works best. A word for manufacturers of wind turbines, such as the Windspire and Swift wind turbines, you are making it too difficult to find where to buy these things or to find out what an average installed price might be. I just spent the better part of two hours TRYING VERY HARD to find pricing and stats for the Swift turbine and I can't find any real answers. The average person would have given up in minutes.
If anyone has real pricing and user data for the windspire or swift turbines, I invite your response.

