[thackney]

a kilogram of hydrogen contains about the same energy as a gallon of gasoline.

Source:
www.hydrogen.energy.gov/docs/cs_distr_steam_methane_reform.doc

The following graph compares to processes. A larger industrial sized facility and an smaller commercial sized facility. The electricity cost are the biggest factor. Industrial rates were $0.045/kWh and Commercial rates were $0.069/kWh for this study.

Source:

Electrolysis: Information and Opportunities for Electric Power Utilities
National Renewable Energy Laboratory
http://www.nrel.gov/hydrogen/pdfs/40605.pdf

This doesn't equate to price at the pump for gasoline, but price at the refinery. Now it needs to be transported, distributed and sold through the retail process. Add the government road taxes and sales taxes.

Then you could compare price to gasoline at your pump.

Now, those electricity prices are cheaper than reality. In 2006 the industrial average price was 6.16¢/kWH and the commercial was 9.46¢/kWH. Scale up the previous chart.

[thackney]

Assuming the smaller commercial sized unit is located in a major market near a place like LA, Houston or Chicago. Then it doesn't need a bunch of distribution cost but is sold only from the facility. Scaling up the electricity cost to 2006 prices hydrogen is $6.77 for an equivalent gallon of gasoline. Of course California has much higher electricity costs than Houston.

How much tax to add?

In Texas, the average is about 38¢ per gallon for gasoline.
California is 64¢. Although California uses a percent sales tax that would go up with the higher price.

http://www.gasbuddy.com/tax_info.aspx

So at least $7 a gallon in 2006. My electricity rates have gone up since then. I suspect most everyone elses has as well.