I like the idea of keeping the "square" look so I went with the best way to pack stuff into a 3x3 square of substations... accumulators fit very nicely into that because they are 2x2, but solars just need a small tweak.
http://imgur.com/a/Jpaa8


As you can see, the solar panels don't fit cleanly, adjust by dropping the substations down.

there is a gap between the substation and the solar panel directly above it, but as you can see its well hidden. You can even add lights in there to brighten it up if you want.

Also fits well into a roboport construction area for fast assembly