That depends on the production and distribution of electricity and not so much the EV.

It's impossible to state any number that would be correct for all cases, but I would guess with a great deal of certainty that it's a hell of a lot less than is lost on production and distribution of gasoline.

And even in some crazy home made diesel generator scenario where the power isn't produced and distributed more efficiently than gasoline, the EV is still about four times more efficient in using the energy after it has been produced and distributed.