Large Californian rooftops to become solar powerhouses

In its quest to achieve 20% energy production from clean sources by 2010, Southern California Edison wants to turn large flat Californian rooftops into useful solar producing spaces. This new project is a followup to a massive wind project. It will eventually produce 250 MW, and installation will be on large commercial buildings at a rate of 1 MW per week starting this august.
Energy production will be enough to supply 162,000 homes and total cost will reach $875 million.
Given that the project takes place in an area blessed with lots of solar energy, there is no doubt it will be a success. Furthermore, boxy buildings offer ideal areas for solar installations and I do not understand why governments do not make solar use compulsory. Surely, there is lots of sparsely populated areas for massive farms, but in densely populated areas any square meter can make a difference.
Link: Treehugger

