The reason to use MPGe is to compare the efficiencies within the vehicle. Not to compare the entire energy cycle.
If you get your electricity from solar panels on your own roof (or feed an equal amount of energy into the grid during the day, and use it during the night to charge your EV), then how would you compare it to a petroleum based fuel car?
Of course, if you raise your own sunflowers of jatropha, or have a diesel excreting bacteria patented, or even if you have a source of old deep frying oil, then you can ask the same question.
The Illuminati Seven has driven
nearly 200 miles on just over 32kWh; which means it got about 217MPGe at highway speeds. The TW4XP has about 85% plug-to-wheel efficiency.
Once you have a renewable energy source, then you don't even have to worry about how efficient it is. We need to move to EV's (and biodiesel) so we can transition away from using billion year old sunshine. We need to use the "youngest" sunshine as possible.
Even
if EV's are worse carbon users than gasoline powered vehicles (they are not worse), then we
still need to make this transition. Because electricity is locally produced, and at the very least, all of that money we pay for it stays in our local economy.
We spend at least $1 BILLION DOLLARS PER DAY on oil from other countries.
We also have had untold subsidies of oil -- not the least of which is oil is traded in US dollars. Remember the "Axis of Evil"? Those three countries changed to trading oil in Euros, and if more countries did this, it would cut us off from the demand for US dollars. We essentially are buying oil with the "profits" of all those oil trades, because they must be done in US dollars.
If all oil was traded in each country's own currencies, then I think we would see the US change it's habits rather quickly.