Nowadays, our dependence on electricity is strong because power consumption has increased considerably in the last years. For that reason, an efficient use of electricity is necessary, especially in public buildings. In order to manage the power consumption, it is vital to measure and monitor the electrical systems. Monitoring can provide advanced visualization and data analysis tools which can help us to achieve energy savings and peak power optimization. In this work, we present a power monitoring system developed for the campus buildings at the University of Leon (ULE) in Spain. This system is based on a three-layer structure. In the server layer, data are acquired from meters installed in the campus buildings. In the middle layer, data are stored and processed. In the client layer, monitoring interfaces, accessible remotely through the Internet, provide both traditional and advanced monitoring tools, based on statistical and data mining techniques. These techniques exploit data in order to find electrical patterns, detect faults and deviations, predict future power consumption, optimize peak power, etc. The data acquired by the monitoring system during 2010 are analyzed. The results from the visualization and data analysis tools, implemented in the monitoring system, are presented. The application of the proposed tools led to economic savings of around 15% and deeper knowledge about the electrical system. (C) 2012 Elsevier B.V. All rights reserved.