<http://www.popularmechanics.com/technology/industry/4199381.html?page=1>
Excellent article on Hydrogen production and use. See the table at the end where they summarize the resources needed to produce enough Hydrogen to displace gasoline as a fuel for passenger cars. Example: 113 million 40-kilowatt solar panel photovoltaic systems, covering 50% of more than 300 million acres – an area three times the size of Nevada — to extract Hydrogen from water using electrolysis. Cost: 22 trillion dollars.
How about wind turbine generators to power the electrolysis? 1 million 2-megawatt wind turbines, covering 5% of 120 million acres, or an area larger than California. A bargain at only 3 trillion bucks.
An interesting read.