Bill,
There are so many variables with a solar install, I wouldnt think it would be a good factory option. Wire size, volt drop for wire length, how many panels are you going to use, what type of controler. The list goes on. Its not that hard to get wires in later, so you or your installer can do it right the first time.
When I did my install I went out and bought a hundered bucks of #10 special handy dandy solar wire, only to find out its too small for the panels I wanted to install.
TimK