Bear in mind that we would need less than 100 quads because much of that figure includes the waste of thermal plants that make our nation's electricity. There is still the energy requirement to produce panels, which many folks think is paid back in several years.
Financial playback takes decades.
It took millions of years of solar energy to make the plants and dinosaurs that made our petroleum, but those 'solar equivalent joules' are different than our present solar energy efforts. I've been asking myself why most people, who are properly concerned about how these energy problems may affect themselves and their families, do not seem to understand that they may need to change their own behavior at home and in the workplace and in using their vehicles in order to help solve this problem. Many scientists and engineers are working daily on ways to achieve greater thermal efficiency in burning coal, oil and natural gas to generate electricity and to raise the efficiency of equipment used in manufacturing and that of appliances and lighting used in commercial buildings and homes. In spite of the many truly amazing technical achievements in these fields, we ought not to forget the critical role for energy conservation. But few, if any, of our elected representatives, seem capable of speaking out on the need to conserve and live more modestly in order to reduce the rate at which we are consuming these valuable, finite fossil fuels and spewing massive quantities of the pollutants emitted from power plants and mobile sources into the atmosphere.