People not acquainted with the world of energy efficiency often mix up these two terms or use them as synonyms. It is a common error, since energy efficiency refers to a better use of the energy resources of our installation with a sustainable approach.
Effectiveness can be defined as the attainment of a goal or result, regardless of the achievement of a better use of resources when attaining that goal or whether the results affect production processes or not.
In turn, efficiency is defined as the relationship between resources used and the results or goals achieved. Consequently, efficiency is achieved when we use fewer resources to attain a goal or achieve better results with the same resources.