This recommended practice describes how to estimate the costs of industrial and commercial power systems, both new and those undergoing expansion or modernization. This recommended practice is restricted to the development of the relative capital cost of industrial and commercial power distribution systems. While this document briefly points out considerations related to total cost or true cost, as well as some technical considerations, other standards and references should be referred to for a thorough analysis of these aspects of power distribution systems. This recommended practice is likely to be of greatest value to the power-oriented engineer with limited experience in this area. It can also be an aid to all engineers responsible for the electrical design of industrial and commercial power systems.