Elected officials throughout the San Diego region are ramping up efforts to form a public alternative to San Diego Gas & Electric, with the city of San Diego leading the way and even the county Board of Supervisors now looking at signing up. California’s three large investor-owned utilities have since 2010 seen more than 8 million customers defect to so-called community choice aggregation programs, from Humboldt to Los Angeles to Solana Beach. However, SDG&E is now facing the largest displacement of a utility’s customer base in the state — raising question about everything from grid reliability to whether the public alternative can deliver more renewable energy as promised.