Solar I purchased - Date's on financials are November but panels not installed by December 31st can I still claim this tax time or must I use installation date?

[JulieCo]

Per the IRS, for purposes of the credit, costs are treated as being paid when the original installation of the item is completed.  Therefore, the panel cost can only be deducted as of when installation is complete.

https://www.irs.gov/pub/irs-pdf/i5695.pdf