http://www.counterpunch.org/wasserman07262010.html

In fact, the National Renewable Energy Lab estimates 100 percent of the nation's electricity could come from an area 90 miles on a side, or a relatively modest box of 8,100 square miles.
If the cost of a 1 square meter solar panel is $600, then the 'mere' 8100 square miles of solar panels would cost a 'mere' $12.5T.

Then another $10T or so for the backup natural gas plants (since nuclear is no no) for those cloudy days.

Fire up the printing presses!