This paper presents an integration mechanism between the prototype customer information system (CIS) and a power engineering planning tool. The aim is to allow the planning staff to use raw data and information available at the CIS in the load forecasts and load increase; hence, leading to reduction of uncertainties related to expected load distribution. The mechanism enables running a large number of simulations with minimum user intervention; storing all the results in the database for easy retrieval, query and classification of suggested system topologies by merit order and acceptance. The paper proposes a new methodology for transmission expansion planning that integrates the information source and power engineering tools.