According to the Turkey's energy supply policy, the main target on electricity generation is to increase the share of renewable-energy usage to above 30% by the year 2023. However, the steps taken to achieve this goal are being realized away from a long-term generation planning. The aim of this study is to examine the situation of renewable-energy sources, considering the Turkey's generation planning and determine its contribution to overall generation together with its electrical and economic consequences. In the study, optimization of generation expansion planning (GEP), which covers the 2012-2027 planning horizon, was performed by using genetic algorithm (GA). The share of renewable sources to be installed for all source types was determined as 8.08%. Furthermore, the effects of reserve capacity level and rate of constraints on sources were investigated. The share of these sources can be increased by encouragements like tax deductions, mandatory quota application or carbon emission trade. (C) 2014 Elsevier Ltd. All rights reserved.