More seriously, how do you calculate the Co2 for EVs? It seems like different power sources used at different times would make calculations like yours almost impossible, since you would need to know when the vehicle was charged and the mix of power sources at the time.

I have a friend who works for the local power company. He told me that at off peak times, our power is almost entirely green. However, at peak times, they use dirty natural gas or coal peaker plants. Even though I don't have time-of-use metered power, I make sure to always charge in the middle of the night for this reason.