willow_hiller
Well-Known Member
The general consensus was "installed and functional" (so yes, when its put on your roof and able to be turned on).
For what this is worth, the federal Office of Energy also agrees.
Found this the other day when searching for an authoritative source to answer this question: Homeowner’s Guide to the Federal Tax Credit for Solar Photovoltaics
The system must be placed in service during the tax year and generate electricity for a home located in the United States. There is no bright-line test from the IRS on what constitutes “placed in service,” but the IRS has equated it with completed installation.