There’s a new map of solar-power cost projections that estimates that San Franciscans could replace PG&E power with local distributed solar as early as 2017. Sfist reported on the map today — and it adds to the clear evidence that San Francisco needs to devote resources to building its own clean-energy infrastructure. Because if the city starts planning to build solar arrays today, and starts designing a plan to help local residents and businesses put solar on their roofs, the day when the cost of that energy will be lower than the cost of PG&E’s fossil-fuel and nuclear power is rapidly approaching.