Article History Keywords Labor Cobb-Douglas production function, capital renewable energy generalized moments method (GMM). Besides traditional production factors, such as labor and capital, one of the inputs used in the production process is energy. Although the use of fossil fuels is more common in many production processes renewable energy sources are increasingly important in ensuring sustainable development. In many countries in the world, the share of renewable energy is the total energy

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... onsumption is very high, including in European Union (EU) countries. The purpose of this study is the investigate the output elasticity coefficients of capital and renewable energy in 12 EU countries by using the Cobb-Douglas production function approach. In this study, the Gross domestic Product these countries from 2000 to 2017, was examined using a generalized method of moments estimation, which used labor, capital, and renewable energy data. As a result of the study, the output elasticity coefficient in the Cobb-Douglas production function was found to be 1.147. This indicates that a 1% increase in labor, capital, and renewable energy increased GDP by 0.598%, 0.446%, and 0.093%, respectively. Among the findings, the relationship between GDP and explanatory variables is statistically significant and economically significant. It is understood that there is a positive relationship between the variables. Contribution/Originality: This study contributes to existing literature by investigating the output elasticity coefficients of capital and renewable energy using the Cobb-Douglas production function approach. INTRODUCTION Along with traditional production factors such as labor and capital, energy is one of the indispensable inputs of production. Fossil fuels, such as oil, natural gas, and coal, are widely used in production processes. However, the use of renewable energy sources has become increasingly widespread in order to ensure energy supply security and to protect the environment based on sustainable development. Today, the share of renewable energy of the total energy consumption is continuously increasing in EU countries. These countries, which do not have sufficient oil, gas, or coal resources, import the energy that they need. Therefore, EU countries have become foreign-dependent on energy, and various energy policies have been established in order to reduce this dependency. Today, the scope of the EU's energy policies can be listed as ensuring effective energy consumption, seeking alternative energy sources, and increasing the production of new and renewable energy sources. The inputs used in production have an impact on the output. In economic theory, the effect of inputs on the outputs is explained by the concept of output flexibility. Output flexibility is defined as the sensitivity of production protection to ensure sustainable development in EU countries. Elements related to the green economy, such as environmental protection, resource efficiency, social integration, and creating new business areas are integrated into various EU policies (Yılmaz, 2014) and are the main aspects regarding renewable energy sources in the EU. Each country in the EU has different energy consumption patterns according to its economic growth rate and economic structure. Table 1 shows the data of 12 selected countries with high renewable energy production positive values of the factor flexibility coefficients of the products show that there is a functional complementarity relation between the inputs. An increase in the amount increases the marginal efficiency of the other inputs. The Cobb-Douglas production function estimated by this state produced results compatible with the theory. It would be beneficial for the selected EU countries that produce the most renewable energy to increase their support policies for renewable energy use.