Are electric cars fuel-efficient and how will it affect the future?

I recently read that EV battery energy density is way lesser than gasoline. Also, most of the power generated today is from non-renewable sources which falsifies all green energy claims. Whereas even though gasoline to motion energy conversion is 33% efficient, it is easy to refill and causes pollution only in localized areas. I am not a proponent of either technology but I am curious to learn how things may pan out in future.