A review of up-to-date waste to energy technologies, their advances and improvements are presented in this paper. The focus is on waste incinerators under conditions of the European Union. Legislation overview, key equipment, ways of dealing with different process streams and tools for evaluating energy efficiency analysis are presented. The principles for maximum energy utilization are also formulated. A comparison of conventional and up-to-date performances of high efficiency flue gas cleaning systems illustrates the development of waste to energy technologies over the past decades.