What is the most used energy source in the next decade ? The world is standing on the edge of energy crisis right now. The cheap and easily used energy sources like woods or fossil fuel are getting less. Beside the lack of quantity, the quality of those carbon based energy sources raise the concerns for the earth environment. The glass-house effect and global climate change demand a fundamental change in the energy sources, which will be used in the next decade. Renewable energy is a promising solution for this issue. Energy collected from sun, wind and water flow is clean and infinite. But the problems for engineer is how to collects enough energy and can supply to user sufficiently and constantly. Even though the renewable energy sources are infinite but the supply heavily depend on weather, which is out of our control. Another solution for future energy is nuclear energy. This type of energy source is very high efficiency and can provide energy continuously. The drawback is security, the world still remember the devastating atomic bombs dropped in Japan 1945 also Chernobyl and Fukushima. Future energy will hardly depend on only one type of source. The way out will be complex and combined using energy sources.