The paper presents the energy use efficiency indicators that are used for the calculation of obtained energy efficiency gains. Calculation and interpretation details are given for the indicator „primary energy intensity”, alongside values recorded in Romania in the past years. The indicator “specific consumption” also plays an important part and it is a feature of the technical efficiency in the use of energy. The French company ENERDATA of Grenoble has established and developed the ODEX system of indicators, which can be used for the calculation of energy efficiency gains. The paper presents the principles of this system. The paper also presents a top-down methodology for the calculation of energy efficiency gains in the end user sectors: household sector, service sector, transports and industry.