Solar tax credit - date

[Ichinco]

We are considering to buy solar panels for our house. The installer said that in order to receive this years (2020) tax credit, the solar system has to be connected and powered up by our electric company. 
There is no information to be found on the internet, regarding if the IRS goes by installment date, bill date or the date the system was actually powered on.
Any info is appreciated.

[DoninGA]

IRS Form 5695, Residential Energy Credits - https://www.irs.gov/pub/irs-pdf/i5695.pdf

For purposes of both credits, costs are treated as being paid when the original installation of the item is completed, or, in the case of costs connected with the reconstruction of your home, when your original use of the reconstructed home begins.

[Opus 17]

The credit is claimed as of the date the item is "placed in service." Placed in service generally means installed, inspected and ready to use.  If the solar is placed in service generating energy for your home, that would count, even if the utility is delayed in connecting it to their system.  

https://www.irs.gov/newsroom/energy-incentives-for-individuals-residential-property-updated-question...