The article presents a review of scientific and technical publications dedicated to one of the possible directions of efficiency improving generation facilities, i.e., the development of multi-generation energy systems. Such systems include energy generation facilities and consumers. This technology is proposed for generation facilities which forced to work in off-nominal conditions during seasonal and daily off-peak periods of electric and thermal loads, which decreases their thermodynamic efficiency. Generation of other produced energy carriers, such as cold, hydrogen, compressed air, etc., is organized together with electricity and heat due to using unclaimed capacities. It allows to provide generation of electricity and heat in the modes close to nominal, and also to organize combined generation of electricity and heat and other produced energy carriers with higher efficiency criteria than with separate generation. Various efficiency evaluation criteria of multi-generation systems are considered, as well as operational features of generation facilities in Russia.