It's impossible to give a single answer to this because it depends on how you define "efficiency", and on what kinds of "fuel" you're talking about. If you def

It's impossible to give a single answer to this because it depends on how you define "efficiency", and on what kinds of "fuel" you're talking about. If you define it as (say) pounds of CO2 emitted per mile driven, then electric cars are about as efficient as gasoline-powered ones if the electricity comes from coal plants, but significantly better if it comes from natural gas. And of course, way better if you have access to renewables.