Some of us care about climate change and want to minimize our own carbon footprint. A year ago, in deciding which new car to buy, I decided to calculate which model would minimize my driving CO2, given my own driving pattern. You may think the largest EV range available in a PHEV would automatically be the best, but there is more to the story, as we will see. I keep careful records of how many miles I drive each day. 64.5% of days, I drive less than 25 miles, 0.5% of days I drive between 400-499, etc. The overall average is 29.3 miles/day. Considering the Prius Prime, I allocated the first 25 miles in each range 'bin' to EV, and remaining miles to gasoline. (I did buy a Prime, and my actual EV range is 25 winter, 36 summer). Adding up all the range bins, this amounts to 16.6 EV miles, 12.7 gasoline miles per day for the Prime. In EV mode, Prime gets 3.95 mi/kWh (EPA est; my experience is 5.0), in hybrid mode a nominal 54 mpg. Dividing, this gives 4.2 kWh/day and 0.23 gal/day. My utility produces 1.24 lb CO2/kWh, and gasoline produces 20 lb CO2/gal. Multiplying, this gives 5.2 lb CO2 from the electricity used, and 4.7 lb CO2 for the gasoline burned, for a total of 9.9 lb CO2/day. Compare this to the Chevy Volt: 45 miles nominal EV range, 3.23 miles/kWh, 37 mpg. Plugging these in would predict 12.45 lb CO2/day with the Volt, given my driving pattern. Now, this is not a huge difference (~20% less), but it is significant. And nothing else I could buy within my price range and that I could take on road trips came close to these two in minimizing carbon. So my choice was clear. Someone who takes more road trips than me would have a comparison even more in favor of the Prime. The most favorable for the Volt would be a person who drives exactly 45 miles/day every day, using the full EV range of the Volt while requiring 20 gasoline miles for the Prime. Even here, the comparison is 15 lb CO2 Prime, 17 lb CO2 Volt. The main thing is, since the Prime is more efficient than Volt both in EV (miles/kWh) and gasoline (mpg), the EV range comparison is less significant. For folks who live where the grid is cleaner, it would be interesting to see how your numbers compare. Obviously, as the grid gets cleaner, the climate case for a higher EV range gets stronger.