Conservation: The Chevy Volt is said to be able to get 230 miles per gallon. That's if it's continually plugged into a fragile and overburdened power grid. Where will you be when the lights go out? Since most U.S. electricity generation is not carbon-free, the Congressional Research Service agrees. The "widespread adoption of plug-in hybrid vehicles through 2030 may have only a small effect on, and might actually increase, carbon emissions," it observes. "If you are using coal-fired power plants and half the country's electricity comes from coal powered plants, are you just trading one greenhouse gas emitter for another?"...