My understanding would be that you simply depreciate the house, including everything that is permanently attached as of the date it is available for rental, as a single item. You use the present fair market value or the adjusted cost basis, whichever is lower. In the case of the solar panels, your adjusted cost basis is reduced by the federal tax credit and any state tax credits.
@Carl @rjs
You don't separately depreciate the house and the solar panels, any more than you would separately depreciate the house and a gas furnace you installed in 2014.
After the house is placed in service, if you make new improvements, they are depreciated separately. But the main house is deprecated as-is. Because you use the FMV or the adjusted cost basis, and your adjusted cost basis include the solar panels (plus any other improvements you have made) that's how you depreciate the solar system.
