The answer depends on many factors, such as cost of material, cost of energy, safety, politics and so on. This paper strives to answer this question from a pure theoretical technical perspective. What's the minimum theoretical energy required to transform the feed materials into hydrogen?
Current technologies to produce hydrogen include:
Exergy concept has been successfully implemented to analyze the maximum power a system can produce or the minimum power to change thermodynamic states. It has been primarily used by mechanical engineers when there is no chemical reaction. However, hydrogen production does involve chemical reaction. This paper will describe how to properly use exergy concept to determine the minimum power required to produce hydrogen. In the end, a comparison summary table will be presented on the minimum power required for each of the technologies.