In recent years, the increasing interest for energy efficiency has multiplied the number of players and the issuing of legislative documents, so the very notion of “efficiency” has taken different meanings in a more or less wide range of definitions, sometimes overlapping between them. These definitions often evoke different concepts such as “energy saving,” “rational use of energy,” “efficient use of resources,” “reduction of consumptions,” etc., in an amalgam shadowed by ambiguous interpretations. This paper proposes a clarification of the different expressions by defining their functional and conceptual boundaries and interrelationships, focusing the attention on the energy aspects, and leaving out other dominions that might govern or accompany that variable, such as, sustainability, competitiveness, economy, etc. The issue is not merely lexical or taxonomic. In fact, the strict definition of a concept defines its area of interest, and the decision-maker, when issuing a measure, should choose from his portfolio of available tools only those consistent with the involved domain.
Part of the book: Innovation in Energy Systems