Solar panels partially paid in 2017, will be fully paid and operational in 2018 - do I enter anything for this on my 2017 taxes, or all for 2018?

I started working with a solar company in summer 2017 to purchase solar panels for my primary residence. I was approved for a loan for the full amount of the project and received the first loan installment (about ? of the total cost) in November. The panels were installed in December, but they still (in Jan 2018) have not been interconnected with the electric company because it was discovered I need a new meter. So the system is not operational, and I have not received the last ? of the loan nor - as a result - paid the company the last ? of the cost.

Do I claim anything on my 2017 taxes? All on my 2017 taxes? Some on 2018? All on 2018?

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