California\u2019s power grid is capable of successfully charging up to 4 million plug\u2013in hybrid vehicles that would cut greenhouse gas emissions and save their owners a total of $6 billion a year in fuel costs, concludes a study by San Diego Gas & Electric released September 24. \u201cThe potential for plug-in hybrids to reduce our dependence on foreign oil, reduce greenhouse gas emissions and reduce consumer expense for transportation fuel is significant,\u201d said Hal Snyder, SDG&E customer programs vice president. The vehicles would be charged during non-peak hours on the grid, the utility said. Though carbon emissions would occur at some of the generating plants that make the electricity to charge the vehicles, studies have shown that plug-ins achieve net reductions in greenhouse gas emissions, particularly when that power is not made with coal. California is relatively light in its use of coal power compared to other states. California utilities also envision the day when plug-ins could be used to store excess renewable energy flowing through the grid and feed it back to the system when it is needed. SDG&E\u2019s study comes on the heels of announcements by major auto makers that they plan to begin selling plug-in hybrid vehicles and other electric models in 2010. Earlier this month, General Motors announced that it plans to roll out its own plug-in hybrid, the Chevrolet Volt, as a part of its 2011 model line up. GM\u2019s announcement came just before Chrysler said this week that it plans to roll out electric vehicles in 2010. Chrysler said it is planning to introduce both a plug-in hybrid and pure battery electric vehicles. SDG&E tested plug-in hybrids on the road for six months and found they get the equivalent of 67 miles per gallon of gasoline. The utility said it plans to replace its corporate cars with plug-in hybrid and natural gas vehicles to cut greenhouse gas emissions from its automotive fleet 15 percent by 2012.