Do the Math: Using physics and estimation to assess energy, growth, options

A common question when discussing solar photovoltaic (PV) power is: “What is the typical efficiency for panels now?”  At 15%, we’re in great shape: it’s plenty good for our needs. Let’s do the math.

http://physics.ucsd.edu/do-the-math/2011/09/dont-be-a-pv-efficiency-snob/