The knowledge regarding how new materials, technologies and innovation are used, as well as their resulting implications to the society is growing. The study aimed at understanding the trend and views of researchers in defining sustainability of renewable energy sources as it is embedded in within the general concept of sustainable development. Related literatures are reviewed and structured interviews were conducted. It was found that sustainability of any system encompasses ecological (biophysical), economic and social sustainability indicators. Therefore, the paper concludes that any source of energy should be evaluated along the identified sustainable indicators. It also attempted to provide an approach for assessing the sustainability of renewable energies to perfectly serve the primary objectives of integrating renewable energy sources in power generation.