There's a good discussion of this topic on Wikipedia, at
Miles per gallon of gasoline equivalent - Wikipedia, the free encyclopedia
You could make a case for heat-equivalent, extractable energy equivalent, dollar-equivalent, or CO2-equivalent methods for comparing gas to electric. I'm inclined to favor CO2 methods, using the average US carbon intensity of electricty, which
I think is .6kgCO2/KWh. With gasoline at 2.421kgCO2/gal, you have 4KWh/gal.
So I'd say Ryland is getting 14mpg(CO2equiv, US average electric mix).
As I've said in other threads, electric cars don't reduce CO2 emissions by themselves. Low-carbon electric generation is required.