The hydrogen could be harvested and sold as a fuel.
Also, lead-acid batteries are not the only option. Some systems use Edison (Iron-KOH) cells.
Me? I'm tied to the grid, no batteries.
Non-food grade oil is cheaper, used french FReedom fry oil has to be disposed of with associated disposal costs, or so I'm told...
Re: Edison cells
From: Alternate Energy Projects Page
http://www.acs.comcen.com.au/nife.html "The downsides are many , low efficiency - may be as low as 50%, typically 60-65%. Very high rate of self-discharge . High gassing / water consumption . High internal resistances , so they can't deliver high currents, and you can get large voltage drops across series cells. High specific weight / volume , High losses in charging and discharging, this will add an extra 25-40% to the size of the solar panels you will need for the same energy usage. In short, they are bloody awful, and think twice if somebody tries to give you a set.
If you are using these sort in a solar installation the inverter needs to be designed for large voltage swings as they discharge . Also when using NiFe's to power DC lighting, you will notice the light intensity fluctuates , this is normal, pay no attention. The only source for new NiFe batteries is from Hungary so freight will also cost you heaps. . . . ."
"The hydrogen could be harvested and sold as a fuel."
This is frought with danger. The hydrogen is coming off the bateries and mixing with air.
The liquification of the hydrogen to seperate it from the other gases will use a lot of power.
I suppose the battery building could be filled with an inert gas but that costs money too.
Ditto on being hooked to the grid
I live in south Texas and it is sunny here much of the year. In between the sunny there is thunder and lightening and hail at times ranging in size from smaller than a pea to larger than a baseball. Any solar panel installed here would need a hail detector that would close the protective shield before impact.