One of the most important considerations in selecting an energy source is: 

The major factor for using energy source is ability to harness energy and that depends on density of energy source. Many factors influence the selection of an energy source, including availability, cost, and ease of use.

The environmental damage that the source will cause in the process of extracting energy from it is also an important factor in deciding or selecting an energy source. The source should emit the fewest harmful gases and cause the least amount of pollution.