Hydrogen fuel cells are very technologically advanced systems that provide an enormous amount of energy without the runoff of pollution. Additionally, hydrogen fuel cells would provide an unlimited resource, as hydrogen can be pulled from nearly any molecule on earth, such as water molecules. Hydrogen by itself yields an astronomical amount of energy, that of which would be incredibly efficient and economical.
Without a doubt, hydrogen fuel cells are efficient and great for the environment. They're much too costly for consumer or regular business use at the moment, though. Only giant corporations and governments can afford to create these cells on a regular basis. Therefore, such fuel cells couldn't be considered economical at present.