In response to climate change, many countries have set renewable energy targets and implemented various policy tools. However, there are contrasting views on the effects of such policy tools, with many deeming international oil prices a potential factor driving renewable energy diffusion. Using an extended logistic growth model, this study aims to investigate this issue and predict the impact of policy tools and oil prices on renewable energy deployment in the electric power sector under various scenarios. The results show that the renewable portfolio standards more significantly influence the diffusion of renewable energy than the feed-in tariff in South Korea's electric power sector and higher international oil prices have led to higher diffusion rates. The forecast indicates that South Korea will generate 40.4-85.9 TW h of renewable electricity by 2024 depending on the scenario. The results also indicate that the renewable electricity diffusion rate will continue to increase by 2024, proving that the current diffusion is in its initial stage. The study concludes with implications for the government, which has a crucial role in the initial phase. (C) 2017 Elsevier Ltd. All rights reserved.