Repealed as of Dec 31, 2017: https://waysandmeansforms.house.gov/uploadedfiles/tax_cuts_and_jobs_act_section_by_section.pdf
That page isn't loading for me. The full text is here, and I couldn't find anything about the credit.
https://waysandmeansforms.house.gov/uploadedfiles/bill_text.pdf
It looks like the credit for solar installations would be extended to 2021 though.
Edit: Disclaimer - I don't speak legalese very well.