The following calculations were carefully done but please, please check them because I want to use them in my book. The calculations say that the conversion factor (practical) for kilowatt hrs to btus is 10447 btus=1 kilowatt hr. I think Murray used 3400 btus, which is incorrect. Roger's number is also incorrect. The total US electricity consumption is about 40 quads or 3835*10^9 kilowatt hrs.
The total cost of the 40 quads al $8 per peak watt=$23.3 trillion. At this high price it seems to me that we should be looking at mirrored arrays. Apartment houses and trees are better bargains.
Data from World almanac
Nuclear electricity= in 2002=780.06 terawatt hours=20.34% of nation's total.
Nuclear energy=8.15 quads energy.
Calculation of conversion factor kilowatt hrs to btus
Conversion factor almanac used=8.15^10^15/780.06*10^9=10447 btus/kwhr
Calculation, sq miles of photovoltaic cells needed to supply nations electricity
Nations total consumption=780.06*10^12/.2034=3835 terawatt hrs or 3835*10^9 kilowatt hrs. 3835*10^9*19447=40.06 quads heat.
Convert terawatt hrs to kilowatt hrs 780.06 terawatt hrs=780.06*10^9 kwhrs
1 sq ft voltaic panel use 100 watts max with 15% efficiency and 15% duty cycle Electric production/yr=100*365*24*.15*.15=19710 watt hrs or 19.71 kwhrs/yr
Sq ft needed=3835*10^9/19.71=1.946*10^11. This is 6979 sq miles or 83 by 83 miles
Calculation of cost of panels needed to supply the nations electricity
One sq ft of panel=100*.15=15 watts peak
Cost of panels per sq ft at $8 per peak watt= $8*15=$120.
Total cost of panels =120*1.946*10^11=$23.3 trillion
One peak watt=.15*365*24=1.314 kwhrs/year. Total power needed=3835*10^9 kwhrs per year. At $8 per peak watt,total cost =8*3835*10^9/1.314= $23.35 trillion.