What is energy efficiency?

Energy efficiency = ratio of output of performance, services, goods or energy, to input of energy for this purpose (Directive 2012/27/EU).

Saving energy = reduce energy consumption, changing behavior by reducing economic activity (Energy Efficiency Plan, the European Commission, March 8, 2011).

Efficient use of energy, increasing energy efficiency = achievement of a unit of product or service without reducing the quality or its performance, while reducing the amount of energy required for this product, good or service (Law 199/2000 regarding the efficient use of energy amended by Law 120/2002).