Why are solar panels only 16% efficient?

They are only about 15% efficient. The best ones yet are in the order of about 30%. There's new research going into this now where people are working out a way of making them spit out far more electrons, or current, for one photon or particle of light. But it's certainly experimental at the moment and the thing is that they're so expensive to build and environmentally costly to build that it's not like Peter's ramp. It's actually costing you far more to build them and run them at the moment than they actually ever pay back, so it's just not energy efficient.