Well to Wheels greenhouse gas equivalence: 15.2KWh = 1 gal gasoline
Well to Plug/Pump energy equivalence: 34 KWh = 1 gal gasoline
Cost equivalence: 18.5KWh = 1 gal gasoline for me today. Wildly variable, changes daily, different everywhere.
Data from Ernie Rogers'
post #85, cost equivalence based on $.12/KWh and $2.25/gal.
So, are you worried about running out of sources of energy, or global warming, or money in your pocket? I don't think it's Ecomodder's place to take up a position on that, so EM shouldn't compare KWh to gal, except to say it's between 15 and 34 KWh/gal.
Not only would it be difficult/impossible to agree on a single KWh to MPGe conversion factor, but it wouldn't be a good idea to boil down EV vs gasser to a single number. They do different things. I'd venture that current-gen DIY electrics are driven shorter distances at lower speeds, and very few of them can complete a road trip. But electrics offer a chance at self-reliance if combined with at-home generation. That applies on a national scale, as well.
I come across as anti-EV at times, and I believe the lifecycle GHG benefits aren't there, but both of those things will change at such a time as the grid shifts to a greener mix and battery technology improves.