Efficiency is one of the most significant elements that characterizes modern technology. However, it is a notion that philosophers of technology do not pay much attention to. Jacques Ellul was no exception to this charge and, although he did not elaborate this concept, he emphasized its importance repeatedly. It is, thus, important to review Ellul's theory in terms of the so-called "efficiency principle." This allows us not only to appreciate Ellul's philosophy, but also to continue developing his insights.