Clearly there is some method of power transfer between the US Segment with the honking big arrays, to the Russian segment.
But since the Russian segment is basically Mir 2 (Zvezda, and an FGB tug which is even older as Zarya), which means it core design was set ages ago, and the US Segment is fundamentally a newer design, how compatible are their power systems?
Though as I think about this, it is likely that the US segment is probably based on the Shuttle experience, which means it is 1970's closer to the Salyut heritage of Mir. So who the heck knows!
Are there transformers/inverters required to transfer power? Or does it all run on a common system?