Over the last couple of years, I have been approached to describe the hydrogen fueling infrastructure or for opportunities related to hydrogen production or distribution. So, here is my point of view for all to know.

• Production of low-carbon (“green”) hydrogen will be essential to replace the ?60 millions of tons of fossil (“gray”) hydrogen used as feedstock for various chemical processes, such as making fertilizer. This is a large decarbonization challenge, and it will be decades before the production of low-carbon hydrogen can catch up. Note that another ?60 millions of tons of fossil hydrogen are used to upgrade crude oil and remove sulfur during refining, but this use of hydrogen will diminish as we transition away from fossil fuel. 
• Molecular hydrogen could be used as an energy carrier, but it is a lousy one, regardless of its color. In fact, the ?120 millions of tons of fossil hydrogen produced now are not used as an energy carrier, except for some small niches, like lunar rockets. Made from low-carbon electricity using electrolyzers, hydrogen is a highly inefficient energy carrier, with only 1/4 to 1/3 of the energy used in the process recovered when the hydrogen is fed to a fuel cell or simply burned for heat. Hydrogen as an energy carrier is also inefficient, as it is difficult to transport and store it, exemplified by the difficulty Nasa had when launching its latest lunar mission. 

As an energy carrier, poor efficiency and effectiveness of hydrogen results in poor economics versus direct electrification of transportation and heat, for most applications. The niche applications where hydrogen could be used will also suffer from low volume in comparison to direct electrification solutions, resulting in worsening economics. Unless you are Nasa, you should probably stay away from hydrogen as an energy carrier. 

Note that hydrogen is not an energy source, but it could be a carrier. While hydrogen is a very common element, it is not an energy source, as it cannot be mined or found in a form that is usable to generate energy. It is an energy carrier when electricity is used to produce molecular hydrogen, which can be converted back to electricity or heat, albeit not efficiently. 

A final note on my personal history: I built an electrolyzer when I was 13 years old. I lit up the resulting hydrogen to make a bang — a rather big bang, it turned out. My mother was not impressed and told me, “never again”. I have a lot of respect for my mother, and perhaps you should too.