UNI CEI 11352:2014 defines the requirements for Energy Service Companies (ESCo). An ESCo certified with this standard is able to offer result-guaranteed contracts to its customers. The Esco is remunerated according to the savings achieved (Third Party Financing). These contracts are becoming increasingly popular in both the industrial and civil sectors because they allow companies to concentrate on their “core” activities, relying on specialists in the sector for the management of auxiliary plants (boilers, cogenerators, inverters, compressed air plants, etc.) and with new financial resources (Third Party Financing, White Certificates). The focus on the efficient use of energy is growing: since the Ministerial Decree of 7 March 2012 that requires compliance with the UNI CEI 11352 standard for Energy Service Companies working with Public Administrations, up to Legislative Decree 102/2014 that provides for mandatory UNI CEI 11352 certification for ESCos offering energy diagnosis services and obtaining Energy Efficiency Certificates for savings achieved in the civil and industrial sectors.