I'm of the minority opinion that efficiency matters. On an individual basis, it does not seem like much, but in the aggregate, it does. An ocean can't exist without many drops of water, and 31% more drops is a lot of ocean.
While the folks that initially got the EV movement off the ground largely because of its long term potential to reduce our impact on the environment are becoming a much smaller percentage of the growing base of EV owners, they occasionally deserve to be heard.
We currently have government mandates forcing ICE automobile manufacturers to increase the efficiency of their offerings, and for good reason. Unfortunately, no such efficiency mandates exist for electric vehicles, even though the well to wheel emissions are generally on par with highly efficient ICE vehicles. As a matter of fact, the Tesla Model S, charging from the grid, is responsible for more greenhouse gas emissions per mile than a Toyota Plug-In Prius (PiP) in every state of the Union except for the 13 with the cleanest electrical grids (Vermont, Washington, Idaho, Oregon, South Dakota, Connecticut, New Jersey, New Hampshire, New York, South Carolina, California, Illinois, and Virginia). See
http://www.climatecentral.org/news/a-roadmap-to-climate-friendly-cars-2013-16318
31% energy consumption difference between two vehicles that accomplish basically the same mission
is a big deal, because that energy comes from somewhere. If it is the electrical grid, it emits (well to wall, on a USA national average basis) 1.52 lbs per kWh. Comparing the most efficient PHEV operating on gasoline (25.9 lb CO
2e per gallon) to the most efficient PHEV operating on electricity, and overlaying the Tesla Model S for comparison:
we see that that, as expected, the BMW i3 REx emits the least of the three up to its EPA range limit of 72 miles. Because of its cleanliness advantage over the Plug-In Prius (PiP), it remains cleaner after its gasoline engine kicks in all the way to 109 miles, where it emits the same greenhouse gasses as the PiP, and above which point the PiP remains the cleanest means of getting around. Note that the Tesla Model S is responsible for more emissions per mile than the PiP at any distance (except in the 13 states mentioned above), but it does equal the emissions of the BMW i3 REx at 184 miles. This is significant, because (on a national average) every single trip you take in a fully charged REx that is less than 184 miles will result in fewer emissions than the same trip in a Tesla Model S 85 kWh. These breakeven points, of course vary - lower for cleaner grids, higher for dirtier ones.
The in-car numbers observed in the OP referenced article are not comparable, as they reflect only a battery to wheel estimate, and are not measured by the same instruments. The only meaningful measurement comparison is wall to wheel, in a carefully controlled test with calibrated instruments and repeated runs, as the EPA carefully oversees measurement of. Those numbers are accurate - 31% advantage for the REx and 39% advantage for the BEV. While I have no doubt that a 90 mph continuous run would lower these numbers somewhat given the Tesla Model S's aerodynamic advantage, the EPA measurements reflect a more reasonable mix of driving speeds.
Just to pre-address the inevitable flood of responses justifying excess consumption because of personally owned photovoltaic systems, keep in mind that we are talking about the marginal case here - that is where your next electron comes from, not the ones you already use. Unless all of your electrical needs are completely covered by your PV system on an annual basis, and you have excess electricity to spare, that 31% excess consumption
is coming from the grid, not your rooftop.
As with any discussion of measures to help our planet, none is more effective than conservation.
