Look at the right side of this homepage for tax incentives by state. It may not be complete, however. For WI it neglects to mention that solar power devices can't be added to property tax. I'magine having 50k worth of solar power panels being taxed as part of your propety! I already pay almost 9k a year!
Solar Power Rocks! Use Solar Energy to Power your Home, your Business, your LIFE!
And don't forget to check with your local utility company.