Chevy Volt

I’d imagine that many of the vehicles will be charged at night, when demand on the grid is lower.

Think about the resulting electric bill this way: what’s easier to increase the efficiency of, millions of gasoline (or any other resource, really) powered engines, or one power plant? As new technologies become available (higher density solar, more efficient wind turbines, fusion power, etc.), we’ll further increase the efficiency and decrease the resulting emissions. Investing in the power grid by purchasing electricity to power vehicles will allow these technologies to come to fruition by consumer demand.