........no electric bill would be nice. New invention. I assume it's still under development, doesn't give a watts/sqft, but I can see the potential.
http://www.ted.com/talks/lang/en/justin_hall_tipping_freeing_energy_from_the_grid.html
http://www.ted.com/talks/lang/en/justin_hall_tipping_freeing_energy_from_the_grid.html