 Hydrogen is not an energy resource , except in the hypothetical context of commercial nuclear fusion power plants using deuterium or tritium , a technology presently far from development . The Sun 's energy comes from nuclear fusion of hydrogen , but this process is difficult to achieve <unk> on Earth . Elemental hydrogen from solar , biological , or electrical sources require more energy to make it than is obtained by burning it , so in these cases hydrogen functions as an energy carrier , like a battery . Hydrogen may be obtained from fossil sources ( such as methane ) , but these sources are unsustainable . 
