Answer
$5.616\times10^{7}GW$
Work Step by Step
We can get from appendix C, the Energy content of oil= 39 kWh/gal
Consumption of oil day in US $=400\times10^{6}gal$
Energy production in each day by US $=\frac{39\space kWh}{gal}\times400\times10^{6}gal$
$\space \space \space \space \space\space \space \space \space \space\space \space \space \space \space\space \space \space \space \space\space \space \space \space \space\space \space \space \space \space= 156\times10^{8}kWh$
By using conversion factors, we can change the units of the above value.
$156\times10^{8}kWh=156\times10^{8}\times10^{3}\times3600\space W$
$\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space=5616\times10^{13}W$
$\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space\space=5.616\times10^{7}\space GW$
