Just follow the money. That motto -- a favorite of investigative reporters and law enforcement -- also happens to be the best way to understand the rapid transformation of solar. As the costs to build and generate solar electricity have plummeted, the amount of installed PV has skyrocketed globally. For many years, following the money trail (i.e., cost reductions) was mostly a matter of tracking falling module prices. But now that panel prices have come down so dramatically, the ongoing and escalating…