Public buildings in Korea have an obligation to supply 10% of the total energy consumption from new and renewable energy sources, which requires proper tools for installation of the energy systems. In this study, a cost-effective method for integration of existing grids with new and renewable energy sources in public buildings in Korea is suggested. A key factor of the method is based on the fact that the unit costs of the products from the energy systems depends on the capacity factor or the utilization factor which is crucially dependent on the interaction between the energy demand pattern for the building and the production time of the specific energy from the new and renewable energy sources. For several public buildings such as two business buildings located at quite different weather conditions, a welfare center and a fire station at different locations, the proper combination of new and renewable energy sources is suggested by detailed numerical calculation based on the hourly energy demand pattern data obtained from field studies for the buildings to minimize the additional cost by installing the energy systems. (C) 2014 Elsevier B.V. All rights reserved.