Solar panels have gotten so cheap that Europeans are building fences out of them, a small sign of how far solar costs have fallen.

• Panel prices have dropped enough that a solar fence costs about the same as a regular fence.
• Even sideways-facing panels earn a little money instead of nothing.
• Cheap panels are the story here, not clever engineering.

Outlook: If solar keeps getting cheaper, expect panels to show up in more everyday places like walls, roofs, and fences.