Urban energy (electricity and natural gas) distribution networks are closely related to the socio-economic and site-specific urban and geographical characteristics of the areas they serve. Overall, these energy systems include generation, transmission and distribution facilities. While generation and production units may be widely dispersed and transmission lines and pipelines may extend over long distances, distribution takes place in urban (built-up) areas, and is thus closely related to urban planning policies and practices. It is difficult and costly to modify these networks after the construction, particularly if underground and therefore their cost structure is a critical component in the decisionmaking of policy makers. If realistic cost functions can be derived for these networks, then infrastructure costs can be forecasted accurately and resources can be allocated in more efficient ways, while providing reliable energy.