I googled this and actually got an answer

How many solar panels do we need to power the US?  

Note: link above was broken, just fixed it.

I ran some of the calculations.  I'm not so sure that his calculations are correct.  The number of hours in the year is 24 times 365.  His number is 9125.  Mine is 8760.   That 365 extra hours from somewhere.  Maybe he multiplied 365 by 25 hours in a day?  He came up with 1643835616 panels.  I won't run those calculations.  Just assume that it is correct.  At 1000 square inches per panel, that adds 3 zeroes to the above number of panels giving total number of square inches.  Dividing this by 4,014,489,600 square inches in a square mile should give number of square miles.  That gives 409.4756 square miles.  You could put that into space, don't you think?