There are four huge incentives for a new roof and solar installation: 1) Federal tax credit, 2) "Bonus" accelerated depreciation, 3) Illinois Solar Renewable Energy Credit (SRECs), and 4) Power company rebate.
Also, the "solar" tax credits are valid for 22 years, they can be used retroactively for the past 3 years, and credits are easily transferrable to other entities or individuals. And power company funding is available for the entire project, including the roof, so zero upfront capital.
It costs nothing for us to show you the incentive numbers, so even if you're just curious, please contact us.