Existing research shows that the short-term impact of free trade on renewable energy development is clear, whereas the long-term influence of free trade on renewable energy development is an open question. To fill the research gap, this work investigates the effects of free trade on the renewable energy considering the effect of population, economy and technology in 186 countries from 1990 to 2015. Free trade is measured by two broad categories: trade volumes and trade taxes. The results show that the influences of free trade on renewable energy in different income levels are heterogeneous: for countries at high and upper-middle income countries, free trade has a positive effect on renewable energy development, but the effect is negative on countries at lower-middle-income countries. Additionally, population increase, economic development and technological progress can promote renewable energy development in 186 countries. (c) 2020 Elsevier Ltd. All rights reserved.