http://www.semiconductor-today.com/news_items/DEC_06/SPECTR_061206.htm

With concentrating solar that is 40% efficient, verified by the National Renewable Energy Lab (NREL).  By collecting heat as well from the same collector, using solar cogeneration, all the heat and electricity for a very energy efficient home could be provided for an initial investment of less than 10k. 

Even without tax credits and other subsidy plans that would give a 5 year or less payback period in most regions of the US.  Because many states offer incentives the payback would be even quicker.  In NJ for instance, the clean energy credits would bring in around 1000 dollars per year.