Sacramento Bee: While many in this troubled economy worry about making investments, Doris Dobkins didn’t think twice about sticking her money on her roof. “Instead of paying PG&E, I’m paying myself,” said Dobkins, a Placer County homeowner who recently spent $36,000 for an electricity-generating solar system. Based on projected savings in her electricity bills, a state rebate and a new federal tax credit, Dobkins expects to recoup her investment in six years. The family anticipates …