Solar power eliminates utility bills in U.S. home

This is an interesting article because:

• It's the first house to be run completely by solar and hydrogen. There are many houses that run with solar and put the excess into the local grid. However this one converts the excess electricity into hydrogen which is then used in the winter. Perfect for those that are not near power grids.
  
• Costs are mentioned.

1. I'd like to know why he needs multiple hydrogen tanks. Perhaps it's a matter of economics, space requirements, shipping problems, whatever. I'd like to know.
2. They mentioned it has a 25yr life expectancy. What needs replacement after 25 years? I know in today's world it's hard to say what the future holds but still I like to plan things that last forever given what we do know.
3. It costs him 500K but apparently it can be done for only 100K which comes out to be about 4K a year instead of the 1.5K you'd be paying the power company. That's not bad at all. Still I'd like to know more about the costs.