[anexprogrammer]

A little over 50% of a roof tile is covered by other tiles to provide the weatherproofing. The square solar part covers nearly all the exposed area.

[onesun]

That's not really how it looks in the pictures on their site. It looks more like they are butted together with no overlap. Also, I'd think you'd want just as much overlap on the long side for weatherproofing. This does raise an interesting question; how are they weatherproofing this installation?