Unfortunately Silicon PV cells are not very efficient. They convert only 14% of the suns energy at best. That and their cost puts flat panel systems out of the reach of most people.
Sunseeker Energy has developed a better system that has an efficiancy ratio of about 36% and is cheaper to produce than flat panel systems. Sunseeker is not in America as yet (Feb 0 but negotiations are under way. They are listing on the German Stock Exchange about mid March 08.
You can find details at
http://www.sunseekerenergy.com