The cogeneration electric power less than 1 MW is defined as small-scale cogeneration.
The one with power less than 50 KW is called micro-cogeneration and is performed by reciprocating engines (internal combustion, micro gas turbines or Stirling cycle engine).
The main difference between the small scale and the micro-cogeneration consists in the fact that in the small cogeneration thermal energy is a secondary product, while the micro-CHP is directed primarily to the production of heat and secondarily to the production of electricity.