TurboTax has a Home Energy Credit section under Deductions and Credits which will walk you through in entering your information on the solar installation for the credit.
To enter Home Energy Credits -
Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credit
Click on I'll choose what I work on (if shown)
Under Your Home
On Home Energy Credits, click the start or update button
Or enter energy improvements in the Search box located in the upper right of the program screen. Click on Jump to energy improvements