Distribution and a network of the small-scale energy systems are investigated as new energy supply methods. If two or more types of small energy equipment are connected to an energy network, it is thought that effective use of exhaust heat, simplification of the transmission network, installation of a backup at the time of a hazard, etc., are possible. However, since the system becomes complicated, optimisation of the arrangement plan of the equipment and the operation plan become difficult. Especially when unstable green energy is intermingled, a precise operation plan is required. The author proposes a new analysis method by installing genetic algorithms into the analysis of the equipment arrangement and the operation plan. Various energy networks including fuel cell, solar power modules, wind turbine generators, diesel engines, geo-thermal heat pumps, etc. are investigated using this new algorithm. The book will be important for those involved in mechanical engineering, power engineering, energy engineering, environmental engineering, etc. who are provided with optimisation of small-scale energy systems.