Non-renewable sources or conventional sources of energy refer to that class of sources of energy which are dependent on materials which are limited in quantity and has the possibility of getting completely depleted in the future if used in very rapid rate. For example, petroleum or coal is available through the deposit which is formed over thousands of years back and thus is limited in quantity to the generation of coal or petroleum takes thousands to millions of years.

Conventional sources of energy cause environmental pollution as emit carbon dioxide and other pollutants on combustion.