Nerf solar panels, hard.

Solar panels are way OP, if you have even a few your batteries simply stay topped off at all times.
I had a fairly long discussion on IRC about this a while back, and I recall a 10/1 nerf being my decision at that point, but I don't have all the rationale handy right now, feel free to discuss and suggest alternatives, but I think solar panels needing a nerf is pretty uncontroversial.