Sources of renewable energies (for example landfill gas, wind, solar energy) are environmentally friendly and electric power generation in South Korea has concentrated on new and renewable energy technologies. The purpose of this paper is to study the economic and environmental influence of renewable energies on existing electricity generation market of South Korea with energy-economic model called 'Long-range Energy Alternative Planning system' and the associated 'Technology and Environmental Database'. Business as usual scenario was based on energy supply planning with existing power plant. And then, the alternative scenarios were considered, namely the base case with existing electricity facilities, the installation plan of different renewable energy facilities, technological improvement and process dispatch rule according to merit order change. in each alternative scenario analysis, alternation trend of existing electricity generation facilities is analyzed and the cost of installed renewable energy plants and CO2 reduction potential was assessed quantitatively. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.